Popularly known as the bechamel sauce has a miriad use cases. My personal favorite begins with making Gratin's. Gratins are French dishes that have a vegetables  baked along with bechamel and cheese. This is a simple recipe. You can modify this by adding herbs of your choice.

A few usage ideas:
Vegetable Gratin's - My favorite is the Calulifower Gratin
Sweet corn with green chillies and Bechamel topped on toasted bread. Delicious!

Makes: 1 cup approximately
Ingredients
3 tablespoons flour
1.5 cup milk
2 tablespoons butter
1/2 cup of grated parmezan cheese
Freshly ground black pepper to taste
Salt to taste

Method

Heat a heavy sauce pan and melt the butter.

On low heat stir in flour with a wire whisk, stirring constantly. Do not allow the mixture to brown.

Gradually stir in milk, whisking constantly. Cook over low heat for 3-5 more minutes until sauce begins to thicken and is cooked.

Season with salt and pepper