Preheat oven to 400°F and lightly grease baking dish with cooking spray.
In a large sauté pan over medium heat; add butter, let melt and add onion, broccoli and cauliflower; season with salt and pepper, cook until tender. In a small bowl whisk together sour cream or yogurt with Dijon mustard. Once cooked, put into medium bowl, add ham, Dijon mixture and half of the shredded cheese. Pour into prepared pan.
Place in the oven and bake for 15 minutes until brown and bubbly.