Leeks, trimmed and cut into 1.5-inch pieces, then halved lengthwise (reserve the tops)
Chicken stock
A few sprigs of fresh tarragon
A little butter
Salt
A splash of sherry vinegar
Cheese Sauce
The reserved leek tops, finely sliced
Butter
Salt and black pepper
Fresh tarragon
Flour
Milk
Grated nutmeg
Mustard powder
Comte cheese, grated (plus more for topping)
Directions
Trim the leeks and cut into about 1.5-inch pieces, then slice those in half. Wash well to remove any grit and arrange snugly in a baking dish.
Heat some chicken stock with a few whole sprigs of tarragon and a little butter (add salt if the stock is unsalted). Lightly salt the leeks and add a splash of sherry vinegar, then pour the stock over the leeks.
Bake at 325F, checking after about 30 minutes, until the leeks are tender.
Meanwhile, make the sauce: melt butter in a pan, add the finely sliced leek tops with a good pinch of salt and black pepper. Cover and cook on medium-low about 20 minutes.
Stir in some more tarragon and a little flour; cook a couple of minutes. Add milk a little at a time until you reach a pourable sauce consistency.
Season with salt, grated nutmeg and a little mustard powder, then stir in the grated Comte until melted.
Spoon the cheese sauce over the baked leeks, smooth it out, and top with a little more grated cheese.
Bake at 400F, checking after about 30 minutes, until bubbly and golden. Let it rest a minute before serving.
