I am a strong believer that simple things are best. Here is a 4 ingredient recipe for you. Use fresh or frozen leeks.
1 leek stalk fresh or frozen, sliced
1/2 cup 35% cream
1 tsp salt
1/2 tsp ground black pepper
In a large skillet melt 1 tbsp of butter. Add the leeks, salt and pepper and cook, stirring constantly on medium-low heat for about 20min, not allowing the leeks to brown. Once leeks become very soft and pleasant aroma appears add the cream and continue cooking so all leeks are covered with the cream for anther 1-2min. Turn heat off and serve as a side dish, pasta topping or spread on bread.
P.S. to make frozen leeks thoroughly clean fresh leek stalk, cut off rough green parts, slice the vegetable and place in a ziplock bag and int he freezer.