Rimmed baking sheet, waffle iron
1 pound dried macaroni
2 tablespoons butter, plus more for greasing baking sheet
1 tablespoon flour
1 cups whole milk
Dash hot sauce, plus more for serving
1 teaspoon mustard
1 1/4 pounds grated cheddar cheese
Maple syrup for serving (optional)
Place pasta in a large pot and cover with lukewarm water by 2 inches. Add 2 tablespoons salt. Bring to a boil over high heat, stirring occasionally, and cook until pasta is tender, about 6 minutes after coming to a boil. Drain pasta.
While pasta cooks, heat butter in a large Dutch oven over medium heat until melted. Add flour and cook, stirring, until pale golden blond. Slowly whisk in whole milk. Whisk in hot sauce and mustard. Bring to a simmer. Reduce heat to low and stir in 3/4 pounds grated cheese. Stir until melted. If smoother texture is desired, transfer to a blender and blend on high speed until glossy and smooth.
When pasta is cooked, add cheese sauce and stir to combine. Pour mixture into a greased rimmed baking sheet and flatten with a spatula. Refrigerate until completely set, about 30 minutes.
Preheat a waffle iron. Carefully cut macaroni and cheese into 8 even squares.
Using a wide spatula, carefully lift one square and plate it on a cutting board. Cover top with 1/4 of remaining cheese. Place another square of macaroni on top of cheese, creating a sandwich.
Place sandwich in waffle maker. Close and cook until golden brown on both sides and cheese has crisped up, about 6 minutes. Remove from waffle iron and serve with syrup and hot sauce. Repeat steps 4 through 6 for remaining waffles.