step 1
1. Preheat the oven to gas mark 3. Grease a 19cm x 23cm (7 1/2in x 9 1/2in) shallow cake tin and line with baking parchment.
step 2
2. Place the plain chocolate and butter in a bowl set over a pan of simmering water and leave until melted. Remove from the heat and beat in the sugar, eggs and vanilla essence, then fold in the flour.
step 3
3. Pour the mixture into the cake tin. Spoon the melted white chocolate over the mixture. Use a skewer to swirl the white chocolate into the mixture, to create a marbled effect.
step 4
4. Bake for 30-35 mins until just firm to the touch. Leave to cool in the tin before cutting into squares.
step 5
Top tip: For a more indulgent pud, serve hot with scoops of ice-cream and warm chocolate fudge sauce. We like English Provender Company's Double Chocolate Fudge Sauce