-
Adjust oven rack to middle position and preheat oven to 375°F.
-
Fill a medium (3 quart) pot 3/4 full with water. Cover and bring to a boil over high heat. When water reaches a boil, add one teaspoon salt and pasta. Stir frequently with a wooden spoon during the first few minutes of cooking. Set a colander in the sink drain the pasta.
-
As soon as you start your pasta, begin your sauce. In a large (5 1/2 quart) pot, melt butter over medium heat. Add garlic and mustard. Cook, stirring constantly, until garlic is translucent, about one minute
-
Switch to a wire whisk. Add sweet rice flour. Cook, whisking constantly, until thick and light brown, about three minutes.
-
In a slow and steady steam, add chicken broth and milk. Whisk until mixture thickens. Cook until mixture is thick and beings to bubble. Add cheese, one handful at a time, until incorporated. Stir gently using a wooden spoon until cheese melts. Sauce should be smooth. Reduce heat to low.
-
Check pasta. When it’s almost tender, drain and return to cooking pot.
-
Add pasta to sauce. Stir to combine. Pour into an 8x8-inch baking pan. Sprinkle breadcrumbs and Parmesan cheese evenly over the top of pasta.
-
Bake until sauce is bubbling and edges are starting to turn golden brown, about or 25-30 minutes. Remove pan from oven and allow to cool for ten minutes before serving.