Here's how to make it:

Halve one of the avocados, remove the pit and scoop the flesh into a mixing bowl. With the tines of a fork, mash the avocado lightly with the onion, garlic, jalapeño, cilantro, salt and cumin. Halve and pit the remaining avocados and score the flesh in two directions so that they resemble cubes. Then invert the skin so the cubes fall into the mixture.

Sprinkle the lime juice over the cubes and mix the entire contents of the bowl lightly until combined, but still chunky. Adjust seasoning with salt and serve with tortilla chips.

Preservation hint:
While working with the avocados, you can prevent them from turning dark by placing the pit in the bowl. Lime juice also helps preserve the green color. When storing in the refrigerator, use plastic wrap pressed directly on the mixture.