Place chips on tray and in oven to packet instructions (about 20 minutes). Shred lettuce, slice tomatoes and onion and lightly toast the brioche buns in a dry frying pan/skillet.
Mix the ingredients together, season salt/pepper and taste. Reserve for later.
Cut the mince into double the amount of portions than people you are serving (so 4 people = 8 portions). Very loosely roll each one into a ball, just tight enough that it holds together and season.
Heat a dry skillet or frying pan for a few minutes on the highest setting until it starts to smoke. Then wipe/brush a little bit of vegetable oil over the pan.
Quickly place one of the round balls of meat into the pan, place the parchment paper on top and use the spatula to flatten the ball into a pattie about 10mm thick; you need to use your other hand to push down on the spatula. Quickly do another one. Fry for a minute, turn them both over (now is the time to add cheese if using) scraping to get them off, then cook the otherside for 45 seconds.
Serve in the bun immediately with burger sauce and condiments or stack all the patties together to keep warm and serve altogether with the chips.
Could try with pork mince, chicken mince, etc. It's a good idea to turn your extractor fan on full when you start cooking these.