Slice each cube of tofu in half and lay it out on kitchen paper. Lay kitchen paper on top and place a heavy tray or chopping board on top to remove some of the liquid. Set aside for 20 minutes.
Divide each half into 4 cubes each. Sprinkle with soya sauce and marinate for 30 minutes. Fry in a hot pan in a little sunflower oil on all sides until golden. Set aside.
Halve the onions and cut each half into 3 pieces. Cut each courgette into 6 pieces. Halve and deseed the peppers and cut each half into 4 pieces. Wipe the mushrooms clean.
Place the onion and courgette in a lidded pot with a little water and a pinch of salt. Steam for 3 minutes until a little tender. Set aside. Place the mushrooms and pepper in the lidded pot with a little water and a pinch of salt and steam for 3 minutes. Set aside.
If using wooden skewers soak in water for 30 minutes to prevent burning when on the barbeque.
Thread a piece of onion, courgette, pepper, mushroom and 2 cubes of tofu onto a skewer. Repeat until all the vegetables and tofu are used up.
You should have 12 skewers of vegetables and tofu.
When the coals are ready brush each skewer with olive oil and place on the grill for 15 minutes each side turning carefully to avoid the tofu falling off.
For the sauce:
Place all the ingredients into a food processor and blend until smooth.
Fill a jug with water and pour into the processor gradually as the sauce is blending.
Add enough water to make a smooth sauce. Heat sauce before serving.