Cut the tofu into a patty with a 3.5" cookie cutter
Slice the patty into two through the middle
Coat one of the slices in the sweet mustard ketchup and leave to marinate while you're getting the rest of whatever you want on your burger ready (lettuce, tomato, cucumber, etc.)
Pre-heat your air-fryer for 3 minutes
Cook the burger on 180C for 20 minutes, turning over half way
Assemble your burger
Recipe by Planet Veggie at https://www.planetveggie.co.uk/easy-vegan-sweet-mustard-tofu-burgers/