2 tbsp unsalted butter (plus more for baking dish)
1 large egg (beaten, room temperature)
1 13 oz. can evaporated milk
1 cup whole milk (room temperature)
8 oz extra-sharp white cheddar cheese (good quality)
12 oz mild cheddar cheese (or another mild cheese like monterey jack, fontina, colby jack, or gouda)
8 oz mascarpone cheese (room temperature)
1½ tsp. salt (or to taste (taste mixture before adding egg))
1 tsp cajun or creole seasoning
½ tsp dry mustard powder (or 1 teaspoon dijon mustard)
⅛ tsp ground nutmeg
fresh cracked pepper (for topping)
Instructions:
Preheat oven to 375°F. Lightly coat a 3-quart casserole dish or 9x13 pan with butter or spray with cooking spray.
Cook macaroni in unsalted water according to package directions, adding 2 minutes to the maximum time listed on the package (I usually aim for 12 minutes). Drain; stir butter into macaroni until butter is melted.
While macaroni is boiling, shred cheese blocks using a box grater or food processor. Combine shredded cheese varieties until evenly mixed.
In a large bowl, whisk together mascarpone and evaporated milk until smooth (there may still be some lumps, which are okay).
Mix in the milk, followed by the salt, creole seasoning, mustard powder, and nutmeg.
Add buttered macaroni to the bowl, followed by 1/2 of cheese. Stir to combine.
Taste mixture to see if seasonings are to your preference and adjust if necessary. Stir in beaten egg.
Pour half of mixture into a 9x13 baking dish, using a spoon to distribute evenly if needed. Sprinkle half of remaining cheese on top, then repeat with remaining macaroni mixture and remaining cheese. Top with some fresh cracked pepper, if you like.
Bake in preheated oven for 25-30 minutes or until cheese on top is melted and filling is bubbling. If you prefer a browner top, place it under the broiler for 2-3 minutes, watching carefully so it doesn't burn. Cool about 15 minutes before serving to let the filling set.