Sweet and Sour Tofu

This an alternative to sweet and sour Chinese dish but with tofu, much healthier. Ingredients: 100g (3 ½ oz) carrots 1 tbsp soya bean paste 300ml (1/2 pints/scant 1 ¼ cups) boiling water 100g (3 ½ oz) fresh root ginger, sliced thinly 1 lemongrass stalk, peeled and finely chopped 10 plum tomatoes, diced ½ green