Leeks are a versatile aromatic vegetable with a subtle onion flavor that can be concentrated or caramelized through baking. As a simple side dish, it is possible to bake leeks in an oven with some olive oil, salt and pepper. The leeks also can be placed in the bottom of a roasting pan so they flavor the drippings, which then can be turned into a sauce. Several recipes bake leeks with cheese or cream, allowing the sauce to reduce and be flavored by the leeks over time and producing a thick sauce around the green stems. Many recipes bake leeks inside salmon or other meat, form it into a baked leek tart, or use it as a filling for a frittata that is finished in the oven.
The simplest way to bake leeks is to chop off the dark green tops, clean the stems and place the leeks in a single layer in a baking dish. Olive oil is then drizzled over the leeks, along with salt, pepper and any other desired spices. Sometimes, whole cloves of garlic can be placed in the pan to create a more complex flavor. This results in soft leeks that have a little color on the outside and will come out of the oven with a thick onion-flavored olive oil sauce.
Another method used to bake leeks is to place them, along with some other vegetables, in the bottom of a roasting pan under a larger piece of meat or fish. The leeks will act as a bed for the main roast, while also slowly giving flavor to the surrounding vegetables and the fat drippings that come off the meat. While cooking, the leeks themselves will almost braise in the pan, sometimes caramelizing if left in the oven long enough.
A more substantial way to bake leeks involves first boiling the leeks in water to cook them a little, and then placing the leeks into a baking pan. The baking pan is partially filled with heavy cream or a mixture of heavy cream and a variety of cheeses, such as grated Parmesan, goat cheese or bleu cheese. After baking in the oven for some time, the cream will reduce, the cheese will melt, and the flavor of the leeks will spread throughout the thick sauce.
As a stuffing, leeks can be baked inside meats such as salmon or beef to provide a light onion flavor and some texture, although the leeks usually are parboiled before being mixed in with the other stuffing ingredients. Leeks also can be used as the main ingredient in an Italian frittata, where their flavor will develop in the oven as the frittata finishes cooking. The leeks can be mixed with cream, cheese, bacon and butter and then cooked in a pie crust to form a baked leek tart.