Equipment Needed
- 9×13 inch baking dish
- Medium saucepan
- Whisk
- Mixing bowls
- Measuring cups and spoons
Step-by-Step Instructions
We start by building our foundation. I preheat my oven to 375°F (190°C) and lightly grease my 9×13 baking dish. In the dish, I combine the cooked chicken and diced ham, spreading them out into an even layer. Then, I sprinkle the shredded Swiss cheese and ¼ cup of the grated Parmesan over the top. Using pre-cooked chicken is the ultimate time-saver here. I’ve used leftover roasted chicken, boiled breasts, but my absolute favorite is a store-bought rotisserie chicken. It’s flavorful, moist, and turns this into a true 30-minute meal. The key is to make sure your chicken isn’t dry.
Now, for the soul of the casserole: the creamy mustard sauce. In a medium saucepan over medium heat, I melt the 3 tablespoons of butter. Once it’s foaming, I whisk in the flour and cook, stirring constantly, for about 1 minute. This cooks out the raw flour taste and creates our roux—the thickening base. Then, I slowly pour in the milk and chicken broth, whisking continuously to prevent any lumps. I keep whisking until the mixture begins to thicken and bubble gently, which usually takes 5-7 minutes. It should coat the back of a spoon.
Once the sauce has thickened, I remove it from the heat. This is when I stir in the flavor powerhouses: the Dijon mustard, garlic powder, black pepper, and that tiny pinch of nutmeg. Don’t skip the nutmeg! It’s a classic pairing with creamy sauces and Swiss cheese, adding a subtle warmth that makes the sauce taste incredibly complex and restaurant-quality. I give it a final taste and adjust the seasoning—sometimes the ham and broth add enough salt, but I might add a little if needed. (See the next page below to continue…)