Step 1

Hold an avocado half in the palm of your hand and, using a butter knife, cut a grid into the flesh. Use a spoon to scoop the flesh into a mixing bowl. Repeat with the remaining avocado halves. Add the lime juice, salt, cumin, scallions, garlic (if using), and jalapeño. Using a fork, mash the mixture until blended but still very chunky. Add the tomatoes and cilantro and fold until combined, being careful not to overmix (you want the guacamole to be chunky). Taste and adjust seasoning with more salt, lime, or jalapeño, if desired. Transfer to a bowl and serve with tortilla chips. If not serving immediately, place a piece of plastic wrap directly over the surface of the guacamole and refrigerate until ready to serve (preferably no longer than a few hours; bring to room temperature before serving).

Step 2

Note: To prepare the jalapeño, use a small knife to slice straight down along one side, removing just the flesh. Turn the pepper and repeat with the remaining sides. All of the seeds and most of the veins -- the extra hot stuff -- should remain in the core. Mince the flesh and reserve the core in case you want to add more heat to your guacamole. Try to minimize contact with the seeds and be sure to wash your hands well after cutting the pepper; definitely do not touch your eyes.