In a medium bowl beat together melted butter, eggs, milk, and maple syrup. Mix in ham, cheese, and vegetables. Cover and refrigerate overnight.
In the morning: Pre-heat oven to 350 degrees F. Butter 11x7x2-inch glass casserole dish. Just before baking, stir the corn muffin mix into the egg mixture and place in casserole dish. (Souffle tends to separate if muffin mix is added the night before.) Place on center rack of oven, bake for 50 minutes. Check to see that center of souffle is firm. If necessary, return to oven for 5 minutes. Serve immediately; however, it will remain warm for up to 1 hour.