Bring a large pot of water to a boil, season generously with kosher salt (about 2 tbsp). Cook pasta to al dente or just under, according to package directions. Reserve 1 cup of pasta water before draining. Return drained pasta to pot over low heat.

Add Old Home Greek Yogurt, milk, cubed processed cheese, and butter to the pasta. Stir to combine. As cheese starts to melt, add in white cheddar, garlic powder, and black pepper. Stir in additional pasta water or milk if needed. Stir until cheese is melted. Taste for seasoning and add salt and pepper as needed.