Preheat the oven to 350°F and coat a 9x13 or 3 quart casserole dish with cooking spray or vegetable shortening. Set aside.
In a medium saucepan, melt the butter. Add the garlic, stirring for 1 minutes until softened. Whisk in the flour until it forms a paste.
Continue to whisk while adding the milk, Dijon mustard, lemon juice, salt, pepper and paprika. Bring to a low simmer and then whisk in the Swiss and Parmesan cheese until melted. Remove from the heat.
Spread the cooked chicken and ham into the prepared baking dish. Cover with the cheese sauce, turning to coat evenly. Set aside if you are making the crunchy topping, otherwise, bake uncovered for 20 minutes.
Crunchy Topping:
In a small bowl, stir together the melted butter, Italian seasoning and garlic powder. Add the melted butter, stirring until it is all wet. Evenly sprinkle over the casserole.
Bake, uncovered, for 20 minutes. Remove and allow to sit for 5 minutes before eating. Top with chopped parsley, if desired.
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