Not Just A Grilled Cheese Sandwich, But a Grilled, Grilled Cheese Sandwich

Ingredients
  1. 4 (1/2-inch slices) hearty country bread
  2. 3 ounces grated extra sharp cheddar cheese (Cabot)
  3. 1 ounce unsalted butter, at room temperature
  4. 1 teaspoon dry mustard
  5. 3 ounces grated Gruyere cheese
  6. 1/2 teaspoon smoked paprika
  7. 1/4 teaspoon freshly ground black pepper