Grilled Mac and Cheese Sandwich

Ingredients

• 8 ounces (230 grams) Macaroni
• 1/3 cup Plain Flour
• 3/4 teaspoon Mustard Powder
• 1/2 teaspoon Garlic powder
• 1/2 teaspoon Kosher salt
• 1/2 teaspoon Black pepper
• 1/8 teaspoon Cayenne pepper
• 6 tablespoons (85 grams) Butter
• 1 1/2 cups (360 milliliters) Whole Milk
• 1 cup (240 milliliters) Heavy Cream
• 1 pound (455 grams) Monterey Jack Cheese
• 4 tablespoons (55 grams) Butter
• 1 teaspoon garlic powder
• 16 slices square Bread
• 8 slices mild Cheddar Cheese
• 8 slices Colby Jack Cheese
• 4 tablespoons (55 grams) Butter