- 5 tablespoons unsalted butter
- 1 small yellow onion, diced small
- 2 garlic cloves, chopped
- 1/3 cup all-purpose flour
- coarse salt
- 4 1/2 cups whole milk
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.