Air Fryer Leek Gratin with Creamy Parmesan Sauce
Leeks deserve a spot at the center of the plate, and this Air Fryer Leek Gratin with Creamy Parmesan Sauce is exactly how I like to introduce them. Thick rounds stand upright in a little baking pan, surrounded by butter, garlic, shallots, white wine, lemon juice, heavy cream and Parmesan, with anchovy paste adding that extra savory something.
I have a thing for introducing friends and family to vegetables they don’t usually cook—and making them completely obsessed. While we were glamping at the lake in our tiny-house camper, I served these leeks and everyone begged for the recipe. Now they LOVE leeks, and they’re a little more open to ingredients like anchovy paste, too!
I still work while we’re at the lake, which is why having an RV kitchen that works for me was so important. These photos are real life in our tiny-house camper—cooking dinner and working on recipes in the little kitchen I love.
What is leek gratin?
A gratin is a dish finished with a browned top, often with cheese or breadcrumbs. Here, I’m working with Parmesan and a creamy sauce rather than a breadcrumb topping, letting the leeks be the main attraction. Think of it as a vegetable side dish with all the appeal of something rich and cheesy.
Leeks belong to the onion family, but their flavor is milder and sweeter than a sharp raw onion. Cooking softens their layers, which is why they work so well with cream. For this dish, I cut them into rounds about 1½ inches tall and stand them on their cut ends instead of slicing them into thin rings.
The ingredients behind the creamy Parmesan sauce
Butter, garlic and shallots give the sauce its savory base, while dry white wine and fresh lemon juice bring acidity to balance the heavy cream. Parmesan adds its own salty, nutty flavor. I use half of the freshly grated cheese in the sauce and add the remaining half once the leeks are soft and the sauce is bubbly, then air fry for another 3–5 minutes to melt the cheese.
And then there’s the anchovy paste! It brings umami, that deeply savory flavor you might recognize from Caesar dressing. Used in balance, it supports the sauce without making the whole dish taste fishy. It’s one of those ingredients that can help someone understand why a sauce tastes so good, even if they can’t quite put their finger on it.
If you’re new to anchovies—or a little hesitant—anchovy paste is such an easy place to start. There are no whole fish to handle or chop; just squeeze out what you need and stir it into the sauce. I love that a little goes a long way, and the tube makes it easy to add that savory flavor to other recipes, especially Caesar dressing.
After opening, cap the tube tightly and keep it in the refrigerator, following your brand’s storage instructions and recommended use-by window. How long it keeps once opened varies by product, so check the label rather than relying on the unopened best-by date.
Because both Parmesan and anchovy paste contribute salt, taste before adding any extra seasoning. Freshly grated Parmesan is a good choice for incorporating into a sauce; packaged grated cheese can contain ingredients that affect how smoothly it melts. Season with salt and pepper to taste.
How to wash leeks without losing those pretty rounds
Leeks can hide grit between their layers, so a quick rinse of the outside isn’t enough. Trim away the roots and tough dark green tops, keeping the white and tender light green portions. Remove any damaged outer leaves and cut the usable stalk into evenly sized rounds about 1½ inches tall, or adjust their height to suit your pan.
Hold each round gently and rinse under cool running water, easing the layers apart just enough to let the water reach any trapped dirt. Check both cut faces as you work. A swish in a bowl of clean water can help loosen grit, but lift the leeks out rather than pouring the sandy water back over them.
If a section is especially dirty, open it further to clean it thoroughly, even if that means it won’t stay perfectly round. Clean leeks matter more than perfect presentation. Drain well and gently pat dry so excess washing water doesn’t dilute the sauce.
Choosing a pan and arranging the leeks
I own both the Ninja Crispi 4-in-1 and the Ninja Crispi Pro 6-in-1, and I’ve made this leek gratin in both. The 4-in-1 is the one I keep at the lake and used for the batch shown here.
I used an 8-inch round baking pan at the lake. Before you begin, check that your pan fits your air fryer with room for air to circulate around it, and that the lid fits securely without touching the food. The pan needs to be oven-safe and heat-rated for your appliance and suitable for use in your particular air fryer according to the manufacturers’ instructions.
Use a solid pan that will hold the sauce, rather than pouring it directly into the air fryer basket. Its sides should leave enough room for the leeks and bubbling sauce without filling it to the brim. An 8-inch pan won’t fit every air fryer, so check the actual usable space, including any handles.
Stand the rounds on their flat cut ends in a single layer, with the concentric rings facing up. Arrange them close enough to help support each other, while leaving small spaces for sauce to settle between them. Keep their height reasonably even so one tall piece isn’t much closer to the heating element than its neighbors.
Cooking the gratin and checking for doneness
The goal is tender leeks with a creamy sauce, deeply browned, crispy caramelized tops and a final layer of melted Parmesan. Browning on top doesn’t tell you whether the centers are tender, especially with thick rounds. Check one of the larger pieces with a small knife or skewer; it should slide through the layers with little resistance, including near the base.
In my Ninja Crispi 4-in-1 at the lake, I remove the bottom tray to fit the pan and use the AIR FRY setting. Mine doesn’t have a selectable degree setting, so I’m sharing the setting I actually use rather than assigning it a temperature. Follow your own model’s instructions for pan placement and whether the bottom tray can be removed.
Air fry the pan of leeks for 30 minutes, then check that the leeks are soft and the sauce is bubbly. Don’t be worried when the tops are very brown—that’s what we want! Those crispy, caramelized leek tops are the best part. Sprinkle with the remaining ¼ cup Parmesan and air fry for another 3–5 minutes to melt it. Any leeks that have floated up can be gently pressed back down into the sauce.
What to serve with creamy Parmesan leeks
I’d pair this rich vegetable side with a simply prepared roast chicken, steak or fish, and let the leeks and sauce do the extra work on the plate. A crisp green salad would be a nice contrast, too. When serving, lift the rounds gently with a spoon and include some sauce with each portion.
If creamy vegetable sides are your thing, my Brussels sprout casserole is another recipe to explore. And for another way to turn a less-familiar vegetable into something people reach for, try my crispy artichoke hearts, which include oven and air fryer instructions.
A few questions before you make it
Wondering whether this is vegetarian? As written, it contains anchovy paste, so it isn’t. If you need a vegetarian version, you would also need to choose a Parmesan-style cheese made with vegetarian rennet.
I’ve made this recipe in both of my Ninja Crispi models. I haven’t tested a conventional oven version or swaps for the cream and wine, so I recommend following the ingredients and method below for this version.
Air Fryer Leek Gratin with Creamy Parmesan Sauce
Equipment
- Ninja Crispi 4-in-1 Use either Crispi model; this is my lake air fryer.
- Ninja Crispi Pro 6-in-1 Alternative to the 4-in-1; I have made this recipe in both.
- 8-inch round oven-safe baking pan
- Saucepan
Ingredients
- 4 medium leeks cleaned and cut into roughly 1 1/2-inch rounds
- 2 tablespoons butter
- 2 teaspoons anchovy paste
- 1 garlic clove pressed
- 1 small shallot finely chopped
- 1/2 cup dry white wine
- 1/2 lemon juiced
- 1 cup heavy cream
- 1/2 cup freshly grated Parmesan divided
- Salt and pepper to taste
Instructions
- Wash the leeks thoroughly between the layers, trim and cut into roughly 1 1/2-inch rounds or a height appropriate for your pan. Drain well and arrange upright in an 8-inch round oven-safe pan that fits your air fryer.
- Melt the butter and anchovy paste in a saucepan. Add garlic and shallot and saute until softened.
- Add wine and lemon juice and cook until reduced by half or more.
- Add heavy cream and 1/4 cup Parmesan. Simmer over medium heat until slightly thickened, about 5 minutes. Season with salt and pepper to taste.
- Pour the sauce over the leeks. Place the pan in the air fryer. In my Ninja Crispi 4-in-1, I remove the bottom tray and use AIR FRY, which has no selectable temperature setting. Follow your model instructions for pan placement.
- Air fry for 30 minutes, until the leeks are soft and the sauce is bubbly. Check a larger round with a small knife; it should slide through easily. The tops will be very brown—those crispy, caramelized leek tops are exactly what we want!
- Sprinkle with the remaining 1/4 cup Parmesan and air fry another 3–5 minutes to melt. Gently press any leeks that floated up back into the sauce.
Notes
I have made this in both the Ninja Crispi 4-in-1 and Crispi Pro 6-in-1. The lake batch used AIR FRY on my 4-in-1, which has no selectable temperature. Cooking may vary with your model and the size of the leeks.
The very brown, crispy caramelized leek tops are intentional. Check that the centers are tender before adding the remaining Parmesan.
