While the tinga is cooking, if you want to make the avocado crèma, tip all the ingredients into a food processor with some seasoning and blitz until smooth, then scrape into a bowl. Serve the tinga with the crema and your choice of tortilla chips, flour tortillas, or rice. Sprinkle over some coriander, crumbled feta and chopped red onion, if you like, and serve with lime wedges on the side for squeezing over.