Use this basic bechamel sauce to make our Rich Chicken and Squash Lasagna, Rich Beef and Eggplant Lasagna, Rich Artichoke and Mushroom Lasagna, or our Rich Spinach and Leek Lasagna.
In a medium saucepan, melt butter over medium. Add onion and garlic; cook until onion is soft, 4 minutes. Add flour, season with salt, and cook, stirring, until mixture is pale golden with a nutty aroma, 4 minutes. Whisking constantly, add half the milk. Add the remaining milk and whisk until smooth. Cook, whisking constantly, until sauce comes to a boil and thickens, 10 minutes. Use immediately.
To store, press plastic wrap on the surface and let cool. Refrigerate in an airtight container, up to 5 days.