Dare I say this Costco Chicken Bake is even better than the original? Crispy pizza dough is filled with a creamy and cheesy sauce, sweet ham, and juicy chicken. It's topped with more cheese, then baked to golden perfection.
Start with the filling. In a pot, melt butter over medium-high heat and add onion. Cook for 2 minutes until edges start to get translucent, then add garlic to cook for 30 seconds.
Whisk in flour to create a roux. Let toast for 1 minute, stirring occasionally. Season lightly with salt & pepper.
Gradually whisk in milk until homogenous. Then stir in chicken broth, lemon juice, and mustard. Season with ½ teaspoon salt and pepper each. Turn heat to medium-low and let simmer for 3-4 minutes to thicken.
Add Parmesan, mozzarella, ham, green onion, and chicken. Turn off the heat and let the cheese melt. Transfer to a heat-safe bowl and refrigerate for 1 hour.
Meanwhile, remove the pizza dough from the wrapper and let sit on the countertop for 30 minutes to rest. Preheat the oven to 475°F and line a baking sheet with foil.
Divide each pizza dough in half. On a lightly floured surface, roll each piece into a rectangle, using fingers to gently stretch out the edges. Be careful not to make it too thin.
Whisk egg with 1-2 tablespoon water to create an egg wash. Set aside.
Divide the filling between the 4 pieces of dough, leaving 1" off all sides. Brush egg wash onto both short ends and one long end. Tuck in the short ends, then the dry edge, topped by the egg-washed long edge. Carefully roll seam-side down and onto the baking sheet. Leave space between each chicken bake.
Brush egg wash all over top and sides of chicken bakes. Sprinkle cheddar cheese on top.
Bake for 20-25 minutes or until browned. Option to broil at the end for extra crispy cheese.