Buttermilk Alfredo Pasta with Chicken and Spinach

I really like this one.  Aside from being delicious, it goes together quickly.

8 oz. uncooked rigatoni pasta

2 tablespoons unsalted butter

1/4 cup flour

1 1/2 cups whole milk

1/2 cup buttermilk

3/4 teaspoon salt

1/2 teaspoon black pepper

4 oz. parmesan cheese, finely shredded - divided

1 5 oz. package fresh baby spinach

4 cups shredded cooked chicken

Cook the pasta according to package directions.  Drain and set aside

Melt butter in a large skillet over medium heat.  Whisk in flour until smooth.  Cook, whisking constantly for 1 minute.  Slowly whisk in the milk.  Cook, whisking constantly, until mixture is thickened and bubbly, about 3 to 4 minutes.  Remove from heat.

Whisk buttermilk, salt, pepper, and 1 cup of the cheese into flour mixture, whisking until cheese is melted.  Stir in spinach, 1 cup at a time until wilted before adding more.

Add chicken and pasta, stir until coated and warmed through.  Sprinkle with remaining cheese.