Mix the ingredients for the vegetable salsa and set aside until you are ready to assemble the burgers.
Beef patties and burgers
Season the mince with the Mexican spice mix and the tomato purée, and mix well.
Shape 4 equal-sized patties and grill or fry them in a little oil until cooked to your liking. Season with a little salt and pepper if needed, and lay the cheddar on top once the first side is nicely browned and the patties have been turned, so the cheese has time to melt.
Warm the burger buns and get ready to assemble your burgers.
Spread the bottom bun with salsa and top it with lettuce leaves and the patty.
Spread a generous layer of guacamole over the patty, then top with crushed tortilla chips and the fresh vegetable salsa.
Spread the top bun with a little salsa, close the burgers and serve.