Roughly chop the onion, serrano or jalapeno, and garlic. Add to the molcajete.
Add a pinch or two of salt. Then, using a pestle or grinder, process the vegetables down to a mush-like consistency.
Roughly chop clean cilantro and pulverize into the onion mixture.
Add fresh, seedless lime and lemon juice to the cilantro/onion mixture. Stir to mix in the liquid.
To start processing the avocado, sliced lengthwise long the center around the pit. Next, twist the two avocado halves apart. Finally, remove the pit and discard.
Using a large spoon, work around the edge of the avocado and underneath to pop out the avocado half.
To dice, slice the avocado first along the horizontal in thirds or two slices as shown in the image above.
As shown above, keeping the avocado in place makes long thin vertical slices down into the avocado.
Now slice down across the avocado, and this will cut the avocado into cubes.
Process the cilantro/onion mixture as before with a pestle or grinder to make a smooth paste with the first two avocados.
With the last two or three avocados, dice and fold them into the guacamole mixture instead of pulverizing them.
(Optional) Add seeded and diced tomato to the guacamole. Check to see if the guacamole needs salt or extra citrus juice.
With a rubber spatula, smooth out the appearance of the guacamole and top with queso fresco/radish slices (optional).
Serve with warmed corn tortilla chips or fresh-cut vegetables.