Scoop out avocado flesh into a molcajete or bowl, add garlic and jalapeño, and mash (with a pestle or a wooden spoon) until the avocados are creamy but still very chunky. Stir in tomato, onion, and salt to taste. Sprinkle with lime juice and cilantro, then stir and taste once more. Add more garlic, jalapeño, onion, salt, lime juice, or cilantro as desired. Serve with tortilla chips.