- 12 carrots, peeled and sliced
- 2 tablespoons brown sugar
- 1 teaspoon celery salt, or more to taste
- 1/4 cup butter
- 1 small onion, minced
- 1/2 teaspoon dry mustard
- 1/4 cup all-purpose flour
- 1/2 teaspoon ground black pepper
- 1 (12 fluid ounce) can evaporated milk
- 4 slices Muenster cheese
- 4 slices mozzarella cheese
- 4 slices provolone cheese
- 1/2 cup dry bread crumbs
- Preheat oven to 350 degrees F (175 degrees C).
- Season carrots with brown sugar and celery salt in a bowl.
- Place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring water to a boil. Add carrots, cover, and steam until tender, 2 to 6 minutes. Remove carrots and reserve hot water.
- Melt butter in a large skillet over medium heat; cook and stir onion until slightly tender, about 3 minutes. Add mustard and flour to onion; cook and stir until flour is golden, about 5 minutes. Measure evaporated milk and enough reserved hot water to make 2 cups; stir into onion mixture. Continue to cook until sauce is smooth, stirring constantly, about 5 minutes. Season with pepper and more celery salt, if needed.
- Layer half the carrots in a 2-quart baking dish. Arrange 2 slices Muenster cheese, 2 slices mozzarella cheese, and 2 slices provolone cheese over carrots and top with half the sauce. Repeat layers. Sprinkle bread crumbs over the final layer of sauce. Cover baking dish with aluminum foil.
- Bake in the preheated oven until cheese is melted, 20 to 30 minutes.