Lemon cream sauce

Here served over ravioli stuffed with cêpes mushrooms, but would also be great over asparagus.

1 Tbsp butter
1 Tbsp flour
1 cup light cream
1 cup milk
1/2 tsp lemon zest
salt and pepper
lemon juice

Melt the butter over med-lox heat in a small saucepan. Stir in the flour and lemon zest, then half of the cream. As it begins to thicken, stir in the other half. Repeat with milk. Season to taste with salt and pepper. Just before serving, stir in a little lemon juice (start with 1 tsp) to taste.