Southwestern Tortilla Soup

Makes 50 servings (3 gallons).

1/2 pound diced butter
9 cups diced Spanish onions
1 cup grated garlic
12 cups fine diced zucchini
4 pounds corn kernels
12 cups diced plum tomatoes
2 gallons chicken stock or vegetable water
1/3 cup chopped cilantro
1/8 cup diced jalape