Spicy Mac and Cheese Soup

Ingredients (10)

• + 2 (7.25 ounce) packages macaroni and cheese mix add to pantry
• ✓ ¼ cup butter
• + 2 cups chicken broth add to pantry
• + 1 (14.5 ounce) can diced tomatoes with green chile peppers add to pantry
• + 1 tablespoon garlic powder add to pantry
• + 1 teaspoon ground cumin add to pantry
• + 1 teaspoon dry mustard powder add to pantry
• ✓ ½ teaspoon ground black pepper, or to taste
• ✓ 1 ½ cups milk
• + ¾ cup sour cream, divided add to pantry