01 -
Boil 2 cups of medium pasta shells in a large pot according to package instructions until al dente. Drain and set aside.
02 -
Melt 4 tablespoons salted butter in the same pot over low heat. Whisk in ¼ cup all-purpose flour, 1 teaspoon garlic powder, ½ teaspoon salt, and ¼ teaspoon black pepper. Cook, whisking constantly, until the mixture is smooth and bubbly, about 1 to 2 minutes.
03 -
Increase heat to medium and gradually whisk in 2 cups whole milk. Continue whisking for 3 to 5 minutes on medium-high heat until the sauce thickens and smoothens, removing any lumps.
04 -
Turn off the heat and stir in 3 cups shredded white cheddar cheese until fully melted and incorporated.
05 -
Return the drained pasta shells to the pot and stir thoroughly to coat them evenly with the cheese sauce.
06 -
Serve warm, optionally garnished with freshly ground black pepper.