Fit a food processor with an S-shaped chopping blade.Chop all the vegetables into relatively small chunks (if you have a smallish food processor, you might want to divide the veg into two batches so as not to overtax your processor).Start with the carrots (densest vegetables first!). Put them into food processor container and pulse until they're broken down into small bits.Add the celery and process.Now add about one-quarter of the salt and process.Add leeks and onions and process.Add another quarter of the salt and process.Add cilantro or parsley and process.More salt, and process. You may also need to scrape the sides of the processor bowl down at this point.Finally, add the tomatoes, garlic cloves, and black peppercorns and process.Then add the rest of the salt and process until it is fully integrated.The finished base should be relatively uniform in consistency and color.Pack into jars and refrigerate for up to four months. For longer storage, freeze for up to a year.