Moussaka has a lush topping of béchamel sauce—or "cream", as it is often called. My light olive oil béchamel is pleasantly tangy, as I substitute yogurt for part of the milk.
• 4 tablespoons olive oil
• 4 tablespoons all-purpose flour
• 1 1/2 cups whole milk
• 1 1/2 cups full-fat plain yogurt
• 1 cup grated aged cheddar or Gruyère cheese, plus more for sprinkling the top
• salt and freshly ground pepper to taste
Whisk together the olive oil and flour, over moderate heat until frothy, about one minute. Remove from the heat, whisk a bit longer and add the cold milk and yogurt. Cook over moderate heat, whisking constantly, and don't worry if the mixture looks lumpy. It will become smooth as it cooks and thickens. When it starts to boil, remove from the heat and stir in the cheese, salt, and pepper.