2 cups whole wheat macaroni
2 ½ cups coarsely grated carrots (about 8 small)
3 cups grated sharp Cheddar cheese
¼ cup (½ stick) unsalted butter, cut into pieces
¾ cup sour cream
¼ cup whole milk
2 large eggs
1 teaspoon kosher salt
¾ teaspoon mustard powder
¼ teaspoon freshly ground black pepper
¼ cup finely grated Parmesan cheese
1. Preheat the oven to 400° F and grease an 8-inch-square baking pan. Arrange a rack in the top third of the oven.
2. Cook the macaroni according to the package instructions in a large pot of boiling salted water. Add the carrots 3 minutes before the pasta is finished cooking; drain well.
3. While the pasta is hot, stir in all but ½ cup of the Cheddar and the butter. In a bowl, whisk together the sour cream, milk, eggs, salt, mustard powder, and pepper. Fold the mixture into the pasta.
4. Scrape the mixture into the prepared pan. Sprinkle the remaining Cheddar and the Parmesan over the top. Bake until the casserole is firm to the touch and golden brown, about 30 minutes.