Take the Tofoo and cut into two slabs, being careful not to break the slab into bits. With a fork gently pierce the slab on each side.
Blitz all the marinade ingredients together and season well. In a flat-bottomed tray add your Tofoo slab and pour over the marinade leave in the fridge for at least an hour.
Heat a frying pan to a medium heat and add the olive oil. Put your Tofoo slabs in the pan and fry for 3 minutes. Turn and fry for a further 3 minutes and then brush with mustard and turn and fry for a minute more (repeat for on the other side).
Place your Tofoo burger in the oven for 15 minutes brushing with the marinade halfway though.
Using the frying pan once again add a little more oil and add your sliced onions fry until soft and golden.
Now toast your burger buns and start to compile your burger. Take the bun bottoms and spread with mayo, add your lettuce, the sliced tomato, your Tofoo burger and then top with the fried onions. Add ketchup and mustard to the bun and squish slightly.