Combine red onion, lime juice, jalapeños, pickling liquid and coriander in a bowl.
Slice the avocados in half and carefully remove the stones. Using a spoon, scoop the flesh into the bowl with the onion mixture. Using a fork, gently mash the avocado into the mixture until just combined. Add extra add-ins now if using.
Season well with sea salt and cracked black pepper to taste. Serve with corn chips or as desired.