Peel and finely slice the shallots. Trim and finely slice the spring onions and chillies, then peel and finely slice the garlic. Peel and finely grate the ginger.
Heat a few drizzles of oil in a large non-stick frying pan. Add the shallots, spring onions, chilli, garlic and ginger and cook, stirring often, over a low heat for 10 to 15 minutes, until soft.
For the marinade, crush both kinds of peppercorns in a pestle and mortar with the coriander seeds and sea salt flakes. Add to the pan with the soy sauce and sugar. Reduce until thick and glossy, then transfer to a small baking tray.
Cut the tofu into 2cm pieces, then thread onto 4 skewers. Place in the tray with the marinade, spoon over to coat and leave in the fridge to marinate for a few hours.
When you are ready, barbecue the skewers till crisp, basting with the marinade and turning regularly.
Use a vegetable peeler to shave the cucumber into ribbons and place in a bowl. Pick, finely chop and add the coriander, followed by the rice wine vinegar and a pinch of sea salt and black pepper. Toss to mix and serve with the crispy salt and pepper tofu skewers.