Finely chop the nuts. Preheat the oven to 180ºC. Beat the eggs, together with the sugar, into an airy mixture. In the meantime, melt 200 g chocolate. Blend the molten chocolate and the lactose-free yoghurt into the egg mixture. Sprinkle the baking powder into the flour and fold into the batter. Pour the batter into a baking tin and bake in the preheated oven for 30 minutes. In the meantime, melt the rest of the chocolate and mix with the oil and chopped nuts. Take the chocolate cake out of the oven. Allow to cool. Pour the chocolate mixture over the cake and sprinkle with the chopped nuts.