Preheat oven to 375 degrees. Grease a 9x13" ceramic baking dish or a large ceramic oval baking dish with 1 tablespoon of the butter, and set aside.

Stir the elbow macaroni into a large pot of boiling salted water. Cook to al dente, about 5 minutes after the water returns to a boil. Immediately drain in a colander and rinse under cold water. Then set aside.

Warm the milk in microwave on high for 20 seconds, or pour it into a saucepan and warm over medium-low heat to just below simmer.

Meanwhile, in a separate pan, melt the remaining 3 tablespoons of butter over medium-low heat. I reuse the Dutch oven that I cook the macaroni in for this step. Reduce the heat to low, and whisk in the flour for 2 minutes, being careful not to let it brown.

Continue whisking, and add the warmed milk in small amounts, taking care to whisk until smooth after each addition. Continue stirring the white sauce until it thickens and comes to a simmer, about 5 minutes.

Remove the white sauce from heat and whisk in the salt, onion powder, black pepper, cayenne pepper to taste, and half of the shredded cheese. Taste the sauce at this point, and adjust the seasoning as needed. Then stir in the drained macaroni.

Spread a third of the macaroni mixture over the bottom of the prepared baking dish. Sprinkle a third of the remaining shredded cheese over the top. Spoon another third of the pasta on top, and layer with another third of the cheese. Finish with the remaining pasta mixture, and then top with the remaining shredded cheese. Sprinkle crushed potato chips over the top.

Bake uncovered for 25-30 minutes, or until golden brown around the edges and bubbling throughout. Let stand for 5 minutes before serving.