Preheat your oven to 375°F. While it heats, butter a 2-quart baking dish and set aside. Shred both the sharp and mild cheddar cheeses (you should have about 2 cups total) and set aside, keeping about 1/4 cup separate for the topping. Cook the elbow pasta according to package directions until al dente, drain well, and set aside. Having everything ready before you start the sauce ensures a smooth workflow.

Add 1 tablespoon of butter, the cottage cheese, and whole milk to a food processor. Add the dry mustard, cayenne pepper, nutmeg, salt, black pepper, and onion powder. Process until the mixture is completely smooth and creamy—this blending technique ensures the cottage cheese integrates seamlessly for a silky sauce without lumps. I find using a food processor here is essential; it breaks down the cottage cheese and distributes the spices evenly throughout.

Pour the smooth sauce base from Step 2 into a large bowl. Add all but 1/4 cup of the shredded cheddar cheese blend to the food processor and pulse briefly just until combined—don't over-mix, as you want the cheese pieces to distribute but maintain some texture. Pour this cheese-enriched sauce into the bowl with the base, then add the cooked pasta from Step 1 and gently fold everything together until the pasta is evenly coated.

Transfer the pasta mixture from Step 3 to the prepared baking dish and spread it evenly. Cover with foil or a lid and bake for 30 minutes—this covered baking allows the dish to cook gently and absorb flavors while staying moist. The pasta will finish cooking and the flavors will meld together during this phase.

Remove the baking dish from the oven and carefully lift off the cover. Give the mac and cheese a gentle stir to distribute the flavors evenly, then sprinkle the reserved 1/4 cup of cheddar cheese over the top. Dot the surface with the remaining 1 tablespoon of butter cut into small pieces. Return to the oven uncovered and bake for another 20 minutes until the top is golden brown and slightly crispy. This final uncovered bake creates that beautiful golden crust everyone loves.

Remove the baking dish from the oven and let it rest for 15 minutes before serving. This resting period allows the sauce to set slightly so it won't be too runny when you scoop out portions. I always find this step makes a huge difference in getting that perfect creamy consistency without it being soupy.