Watermelon Gazpacho

Name: Watermelon Gazpacho
Ingredients: 12 cups seedless watermelon cubes (8 cups cut into 1/2-inch cubes and 4 cups cut into 1/4-inch cubes, divided); 2 large red tomatoes (seeded and diced); 1/4 cup chopped fresh mint (plus sprigs for garnish); 1 large English cucumber (peeled, seeded and diced); 1/2 cup diced red onion; 2 serrano chiles (seeded if desired, minced); 2 tablespoons extra-virgin olive oil; 1 tablespoon red wine vinegar (or to taste); Salt and freshly ground black pepper (to taste); Mint sprigs for garnish