Spicy Meatball Soup

First prepare the meatballs. Sauté the onion and garlic with salt and pepper to taste in a hot oiled frying pan for about 5 minutes until soft and lightly colored, adding the red pepper flakes after a minute or two. Place the beef in a large bowl and add salt and pepper. Make a well in the center of the meat. Put the breadcrumbs in a separate bowl and moisten with the milk. Add salt and pepper, then stir the breadcrumbs and onion mixture into the beef and mix until just combined. With wet hands, shape the beef mixture into small balls slighly larger than a golf ball. Transfer to a lightly greased plate or baking sheet and chill for 30 minutes until firm. Put a little olive oil in a frying pan and cook the meatballs over a medium-low heat for about 10 minutes until evenly colored on the outside. Add the chipotle chile paste (or chipotles in adobo) and stir over high heat. Add the canned tomatoes, oregano, and stock. Bring to a boil, then lower the heat. Season with salt and pepper and gently simmer for 20 minutes until the meatballs are cooked through and the soup has thickened slightly (this can be done in advance, then left overnight for the flavors to develop). Before serving, add the corn and zucchini and cook for 3-4 minutes, until both are tender. Serve the soup garnished with the tortilla chips, cilantro, and jalapeno peppers.