"Instant" Mac and Cheese

Ingredients (10)

• + 2 cups whole milk add to pantry
• + 1 teaspoon kosher salt, or more to taste add to pantry
• + 1 pinch cayenne pepper add to pantry
• + 1 pinch dried mustard add to pantry
• + 1 very small pinch ground nutmeg add to pantry
• + 3 tablespoons unsalted butter, divided add to pantry
• ✓ 1 cup elbow macaroni
• + ½ cup panko bread crumbs add to pantry
• + 1 cup freshly shredded sharp Cheddar cheese add to pantry
• + 1 cup freshly shredded white Cheddar cheese add to pantry