Heat a frying pan and dry fry the walnuts until browned. Remove from the heat and allow to cool slightly. Place in a food processor with the salt and grind coarsely.
In a bowl, mix the soya mince, stock powder and 300ml boiling water. Allow to soak for 10 mins. Drain in a sieve and press out any liquid.
Heat the oil in a saucepan and sauté the onions, garlic and soya mince for 5 mins. Stir in the tomato purée, then add 100ml water and the tomatoes, breaking them up with a wooden spoon.
Add the red wine, agave nectar and oregano and stir. Season with salt and black pepper and simmer for 15-20 mins.
Cook the spaghetti in boiling salted water according to the pack instructions. Drain and toss with the sauce. Garnish with the walnuts and basil leaves.