Heat oven to 350*. Spray a 2-3 quart Casserole dish and set aside.
Heat a heavy bottom skillet over medium heat for 2 minutes. Add the oil and chopped onions and stir-fry until golden, about 3 minutes. Add the garlic and cook 1 more minute.
Spread the onion garlic mixture on the bottom of the baking dish and top with the tater tots.
In a bowl, combine the soup, milk and cheese. Pour the soup mixture over the tater tot layer. Bake the Casserole on the center oven rack for 30-40 minutes until cheese is bubbly and golden. Top the Casserole with chopped parsley if desired.
You can add 2 cups cooked & chopped rotisserie chicken or seasoned cooked ground beef over the onion layer. Add 10 minutes to baking time.