Slice the tofu into roughly 1cm-wide sticks and lay them evenly on a board.
Sift the cornflour generously over the tofu, turning to coat all sides well. This is what gives the tofu its crispy coating, so don’t be shy.
Heat enough vegetable oil to coat the base of a medium frying pan over a medium-high heat. Once hot, add the tofu and fry for around 5 minutes, turning regularly until golden and crisp on all sides. Remove and place on kitchen paper to drain.
Carefully discard the excess oil from the pan and return it to the heat. Add the lemon juice, orange juice, sweet chilli sauce and soy sauce. Bring to the boil, then simmer for about 5 minutes until reduced and slightly syrupy.
Add the crispy tofu back to the pan and cook for a further 5 minutes, turning occasionally so each piece is fully coated in the sauce.
Serve immediately, sprinkled with spring onion and sesame seeds. Delicious on its own or served with rice.