Holiday Leftover Breakfast Casserole

Name: Holiday Leftover Breakfast Casserole
Cuisine: American
Ingredients: 8 large eggs; 2 1/2 cups whole milk; 1 tablespoon Dijon mustard; 1 tablespoon fresh parsley, minced, plus more for garnish; 1 tablespoon fresh chives, minced, plus more for garnish; 1 teaspoon kosher salt; 1/2 teaspoon black pepper; 1/4 teaspoon paprika; 6 cups leftover slightly-stale french or italian bread, cut into 1/2” cubes; 1 pound leftover baked ham, cut into small cubes; 1 cup sharp white cheddar, shredded; 1/2 cup Gruyere cheese, shredded