twice baked potato soup

Ingredients

• 1 medium onion, chopped
• 2 tablespoons butter
• 32 ounces chicken stock
• 1 can cream of chicken soup
• 1 can cream of celery soup
• 1 1/2 cups whole milk (or 2% works fine)
• 1 teaspoon salt
• 1 teaspoon black pepper
• 32 ounces bag frozen cubed hash browns
• 1-2 cup leftover mashed potatoes, or omit if you don't have
• 1 pound velveeta cheese
• 1/2 pound bacon
• 3 - green onions, chopped
• 8 ounces sour cream