Classic Tater Tot Hotdish Recipe

Ingredients

• 1/2 cup unsalted butter, divided
• 2 carrots, finely chopped
• 2 stalks celery, finely chopped
• 1 large onion, finely chopped, divided
• kosher salt
• 3/4 cup all-purpose flour
• 3 cups whole milk
• 2 tablespoons chicken, vegetable or beef soup mix
• freshly ground black pepper
• 2¼ pounds ground beef
• 9 ounces frozen peas or corn
• 1½ pounds Tater Tots
• shredded cheese (optional)
• chopped parsley, for garnishing (optional)
• ketchup, for serving