Starring two types of cheese—cheddar and Jack—this rich sauce from Kurt Beecher Dammeier's "Pure Flavor" cookbook is the secret-weapon ingredient in his World's Best Mac and Cheese.
Melt butter in a heavy-bottomed saucepan over medium heat; whisk in flour. Continue whisking and cooking for 2 minutes.
Slowly add milk, whisking constantly. Cook, stirring frequently, until sauce has thickened, about 10 minutes. Remove from heat. Add cheeses, salt, chile powder, and garlic powder. Stir until cheese has melted and all ingredients are well incorporated, about 3 minutes. Use immediately or refrigerate up to 3 days.
To reheat sauce, place in a saucepan over low heat, stirring frequently, until heated through.