Marco Pierre White's prawn risotto with basil recipe

Ingredients

• 1 stock pot/cube
• 15 g butter
• 1 tbsp olive oil
• 1 onion or 2 shallots, finely chopped
• 400 g risotto rice
• 125 ml dry white wine
• 4 handfuls basil leaves
• 400 g raw, headless king prawns, peeled and chopped
• 100 g sun-blush tomatoes, chopped
• 1.5 tbsp mascarpone cheese