1-First Step: Preheat oven to 350 degrees F and spray a 9×13 casserole dish with cooking spray.

2-Second Step: Layer shredded rotisserie chicken evenly on the bottom of the casserole dish. This helps your chicken casserole recipe bake evenly, so every bite gets that tender chicken base.

3-Third Step: Layer cubed ham evenly on top of the chicken layer. If you’re using leftovers, try to cube them similarly for a more even bake.

4-Fourth Step: Make the cheese sauce. Melt 4 tablespoons butter in a saucepan over medium heat. Sprinkle in 1/4 cup all-purpose flour and cook for 1 to 2 minutes until the mixture looks dry and clumpy.

5-Fifth Step: Slowly whisk in 2 cups milk, then add 1 tablespoon Dijon mustard, 1 tablespoon lemon juice, 1/2 teaspoon garlic powder, and 1/4 teaspoon salt (adjust later if you want). Simmer for 3 to 5 minutes, whisking constantly, until thickened.

6-Sixth Step: Remove from heat and stir in 1 1/4 cups shredded Swiss cheese and 1/4 cup grated Parmesan cheese until melted. Taste and adjust salt as needed so your cheesy chicken casserole hits that perfect balance.

7-Seventh Step: Pour the cheese sauce evenly over the chicken and ham layers in the casserole dish. Make sure it reaches the edges so you don’t end up with dry spots.

8-Eighth Step: Mix 1 cup Panko bread crumbs and 2 tablespoons melted butter in a small bowl. Sprinkle the mixture evenly over the top of the casserole for that classic cordon bleu casserole crunch.

9-Ninth Step: Bake casserole uncovered for 30 to 35 minutes, until breadcrumbs are golden brown and the filling is bubbly.

10-Final Step: Allow the Chicken Cordon Bleu Casserole to cool for 5 to 10 minutes before serving. You can serve it alone, or spoon it over pasta or rice to make it even more filling.