Preheat oven to 375°F. Remove the tater tots from the freezer to slightly thaw, while you prepare the filling
Place bacon in a 10-inch skillet over medium heat. Cook until crispy and golden brown, 3-4 minutes on each side. Remove and place on a paper towel. Chop when cooled.
Leave 2 tablespoons of bacon grease in skillet and add chopped Onion. Cook until slightly clear, about 4 minutes. Add Garlic and cook for an additional minute.
Add in ground pork sausage or ground beef and cook, breaking it into small pieces with a wooden spoon. Cook until it browns and is cooked through (about 10 minutes). Drain off the excess fat, leaving in as much as you prefer for flavor and consistency. Remove the skillet from the heat.
Stir in the soup, milk, butter, salt, and pepper, and blend with a wooden spoon until smooth.
Fold in spinach, then corn, and stir.
Sprinkle cheddar cheese evenly across the top of the casserole.
Place the frozen tater tots on the top of the casserole in a single layer, arranging them in concentric circles, starting from the outside of the pan and working toward the middle.
Sprinkle the tater tots layer with Parmesan cheese.
Bake until tater tots are golden brown and filling is cooked and bubbly, approx. 30-35 minutes.
Remove from oven and sprinkle the chopped Bacon over the top. Let the casserole rest for 5 to 10 minutes.
Garnish with sliced green onions, if desired, and serve.