In a bowl, using the back of a wooden spoon, thoroughly mash the first four ingredients into a juicy paste using salt as a grinder.
Holding avocado in the cup of the hand, split the avocado in half lengthways and remove the seed. Slice avocado lengthways in approximately ⅛-inch strips, then across forming a grid. Cut through the flesh only, not into the skin. Scoop avocado out of the skin with a spoon.
Add avocado to the paste and thoroughly mix. Add onion, jalapenos, cilantro, and tomatoes and fold. Add jalapeno chilies and salt to taste. Serve with tortilla chips. Makes 4 servings.