Preheat the oven to 180°C/350°F.

Place the butter in a bowl, add sugar and beat together till the sugar dissolves. Melt one hundred and seventy grams of chocolate in the microwave oven for one minute and whisk till smooth. Add to the butter mixture and mix well. Break the eggs into a bowl and whisk them well. Add the vanilla essence and whisk again. Sift the flour and baking powder into the bowl with eggs and whisk with a hand blender.

Add the butter-sugar-chocolate mixture and whisk again. Add the walnuts and mix. Pour the batter into silicone moulds and place them in the preheated oven. Bake for twenty to twenty five minutes. When done take them out and set aside to cool a little.

Heat the cream and the remaining chocolate in separate bowls in the microwave oven. Whisk the chocolate and add the cream and whisk again till well blended.

When the brownies have cooled a little spread the truffle over and serve.