Ingredients
1 1/2 tablespoons unsalted butter
2 tablespoons all-purpose flour
1 teaspoon Dijon mustard
2 cups whole milk
Pinch of freshly grated nutmeg
1/2 cup shredded Gruyere cheese (about 4 ounces)
Coarse salt and freshly ground pepper
Preparation
Melt butter in a medium saucepan over medium heat until foamy. Add flour and cook, stirring frequently, until mixture is pale golden and has a slightly nutty aroma, about 5 minutes. Stir in Dijon.
Whisking constantly, pour in 2 cups milk and whisk until smooth. Cook over medium-high, whisking often along the bottom of pan, until boiling, about 7 minutes.
Reduce heat to maintain a simmer. Add nutmeg and cook, stirring occasionally, until sauce thickens to the consistency of thin yogurt, about 10 minutes. Stir in Gruyere. Season with salt and pepper.
