Ingredients

Kosher salt

1 lb. shells or elbows

4 tbsp. unsalted butter 

1/4 c. all-purpose flour

2 c. whole milk

1 c. heavy cream or half-and-half

1 1/2 tsp. dry mustard or Dijon mustard

3/4 lb. sharp white cheddar, shredded (4 c.)

1/4 lb. white American cheese (about 5 slices)

Preparation

Step 1In a large pot of boiling salted water, cook pasta until al dente according to package directions. Drain.Step 2Add butter to pot and melt over medium heat. Add flour and whisk to form a thick, smooth paste without lumps. Cook until fragrant but not browned, 2 minutes. Reduce heat to medium-low and add milk, cream, mustard, and 1 teaspoon salt. Continue to whisk until sauce begins to bubble and thicken, about 5 minutes. Step 3​​Add cheeses and stir with a rubber spatula or wooden spoon until all cheese is melted. Add cooked pasta and stir until fully coated.