Put the minced onion, lime juice, chipotle chilies and the 1/2 tsp. salt in a small bowl, and smash with a pestle or fork to a coarse paste. Cut the avocados in half, remove the pits and scoop the flesh into the bowl. Add the minced cilantro and mix and mash, leaving some lumps. Taste and adjust the seasonings with salt.
Sprinkle the guacamole with the cilantro leaves and/or chopped onion and serve immediately, if possible. To keep the guacamole at room temperature for up to 1 hour, cover with plastic wrap, pressing it directly onto the surface. To keep the guacamole for up to 3 hours, do not add the cilantro until just before serving, and cover and store in the refrigerator. Makes about 2 cups.