1-First Step: Preheat and Prep the Dish Start by preheating your oven to 350°F (175°C) to ensure it’s nice and hot when you’re ready to bake. Grease a 9×13-inch casserole dish with a bit of butter or oil to prevent sticking, which makes serving a breeze. This initial step sets the stage for a casserole that cooks evenly and comes out bubbly.

2-Second Step: Layer the Main Ingredients Once your dish is prepped, layer 5 1/2 cups of shredded rotisserie chicken evenly across the bottom for a solid base. Add 2 cups of cubed ham on top of the chicken to build those classic flavors we love in chicken cordon bleu casserole. If you’re adapting for dietary needs, like using turkey instead, this is the spot to swap it in for a lighter twist.

3-Third Step: Make the Cheese Sauce Now, create the heart of the dish by melting 4 tablespoons of butter in a saucepan over medium heat. Sprinkle in 1/4 cup of all-purpose flour and cook for 1-2 minutes until it turns dry and clumpy, forming a roux that thickens your sauce. Slowly whisk in 2 cups of milk, then stir in 1 tablespoon of Dijon mustard, 1 tablespoon of lemon juice, 1/2 teaspoon of garlic powder, and 1/4 teaspoon of salt.
Simmer the mixture for 3-5 minutes, whisking constantly until it thickens to a creamy consistency. For variations, if you’re going gluten-free, use cornstarch here to keep things smooth. Once thickened, remove from heat and mix in 1 1/4 cups of shredded Swiss cheese and 1/4 cup of grated Parmesan cheese until fully melted. Taste and adjust seasoning as needed for that perfect balance.

4-Fourth Step: Assemble the Casserole Pour the cheese sauce evenly over the layered chicken and ham, making sure every bite is coated in that delicious mixture. In a small bowl, combine 1 cup of Panko bread crumbs with 2 tablespoons of melted butter to make the topping. Sprinkle this mixture over the casserole for a crispy finish that contrasts the creamy inside.
If you’re prepping ahead, stop here and refrigerate without the topping to save time later. This step is versatile, allowing you to add veggies or adjust portions based on your family’s preferences.

5-Final Step: Bake and Serve Bake the casserole uncovered for 30-35 minutes until the topping turns golden brown and the dish is bubbly around the edges. Let it cool for 5-10 minutes before serving to help it set, making it easier to dish out. For a complete meal, serve it over pasta or rice as suggested, and feel free to pair it with sides from other recipes like our oven-baked chicken legs for a fuller spread. This final touch ensures your chicken cordon bleu casserole is not only tasty but also tailored to your needs.