Make a chunky guacamole by roughly mashing together the avocado, lime juice, chilli and spring onion in a small bowl. Cover and set aside in the fridge.
Heat a frying pan over a medium heat, add the chorizo and cook until crisp and browned. Remove the chorizo with a slotted spoon on to kitchen paper and set aside.
Bring a pan of water to the boil over a high heat, then reduce to a low simmer. Add the vinegar and gently break the eggs into the water. Cook for 2 minutes. Remove with a slotted spoon on to kitchen paper.
Meanwhile, toast the muffin halves. Mix most of the cooked chorizo into the guacamole and spread over the muffin halves. Top with the sliced tomatoes and poached eggs. Scatter over the remaining chorizo and season with freshly ground black pepper.