Preheat the oven to 375 degrees. Remove the tater tots from the freezer to let them thaw slightly while you prepare the filling. Heat a large skillet over medium heat. Add the bacon and cook until golden brown and extra crispy, 6-8 minutes. Remove to a paper towel lined plate and leave the grease in the skillet. Add the onion to the skillet and cook until slightly softened, about 4 minutes. Add the garlic and cook 1 more minute. Add the ground beef and break into small pieces with a wooden spoon. Cook the meat until no pink pieces remain, 6-8 minutes. Remove from the heat. Stir in the soup, milk, salt and ½ teaspoon black pepper and mix until smooth. Fold in the spinach to wilt slightly, then the corn. Sprinkle the cheddar cheese evenly over the top of the casserole. Place the tater tots on top in a single layer, arranging them in concentric circles (or just toss them on and push them very close together.) Sprinkle the top with parmesan cheese and the additional 1/4 teaspoon of black pepper.  Bake 30-35 minutes until the tater tots are golden. Remove from the oven and crumble the reserved bacon over top. Let rest 5 minutes. Top with chopped chives or scallions and serve.