Cut the avocados in half and remove the pit.

Using a spoon, remove the flesh from the skin.

Place the red onion, serrano chile and cilantro in a molcajete and mash them. (A molcajete is a traditional Mexican mortar and pestle made of volcanic rock. If you don’t have a molcajete you can use a fork to mash.)

Add the avocado and fold it in. Add the tomatillos.

Place the guacamole in a serving dish and top with the cheese.

Serve with lime wedges and totopos, fried tortilla chips.