Mix the Sauce: In a large mixing bowl, combine milk, honey mustard, Dijon mustard, garlic powder, and black pepper. Whisk until smooth.
Combine Ingredients: Add the diced ham, cooked pasta, mixed vegetables, and half of the cheddar and Swiss cheese to the sauce. Stir until everything is evenly coated.
Prepare Baking Dish: Lightly grease a 9x13 inch (3-quart) baking dish with olive oil.
Assemble the Casserole: Pour the ham and pasta mixture into the prepared baking dish. Spread evenly to ensure even cooking.
Add Cheese and Topping: Sprinkle the remaining cheddar and Swiss cheese on top. If desired, add breadcrumbs to create a crunchy topping.
Bake: Place the casserole in the preheated oven and bake for 30-35 minutes or until the cheese is bubbly and golden brown.
Cool and Serve: Remove the casserole from the oven and let it cool for about 5 minutes before serving.