Bring a saucepan of water to the boil and stir in the bicarbonate of soda and salt. Slice the tofu into roughly 1cm thick slices, then carefully lower them into the water. Boil for 8 minutes before gently removing and patting dry.
While the tofu cooks, finely slice the carrot, onion, chilli and cucumber. Remove the soft seeded centre from the cucumber before slicing. Toss everything together with the vinegar, sugar and salt, then leave to pickle for at least 10 minutes.
Heat a large frying pan over a medium-high heat with a little oil. Fry the tofu for a few minutes on each side until golden and crisp. Remove from the pan and set aside.
Add a little more oil to the pan if needed, then fry the garlic and lemongrass for 1–2 minutes until fragrant. Stir in the tomato paste and cook for 2–4 minutes to deepen and caramelise the flavour. Add the sriracha, soy sauce, vinegar, ketchup (if using) and sugar. Stir together until you have a thick, jammy sauce. Add a splash of water to loosen if needed. Return the tofu to the pan and gently toss until every piece is coated.
Split open your baguette and spread with mayonnaise and pâté. Layer in the tofu, pile on the pickled salad and finish with plenty of fresh coriander. Eat immediately, ideally somewhere sunny… maybe even on a beach.
