Heat oven to 375 degrees.
In a large mixing bowl, combine bread, milk, eggs, mustard, garlic powder and paprika. With electric mixer, beat at medium speed 1 minute or until smooth. Stir in Spam, 1 cup cheddar cheese, and onion. Pour into a greased 12- by 8-inch baking dish.
Bake 25 minutes. Top with remaining cheddar and Monterey Jack cheese. Bake 5 minutes longer or until cheese is melted. Let stand 10 minutes before serving.
This recipe yields 6 servings.
Content per Serving: Calories 434; protein 28 g; total fat 28 g; carbohydrates 19 g; sodium 1077 mg; cholesterol 203 mg.
Per serving: 326 Calories (kcal); 20g Total Fat; (56% calories from fat); 19g Protein; 17g Carbohydrate; 149mg Cholesterol; 506mg Sodium Food Exchanges: 1 Grain(Starch); 2 Lean Meat; 0 Vegetable; 0 Fruit; 3 Fat; 0 Other Carbohydrates