In a bowl or jug, whisk together the flour, milk and egg until you have a smooth batter. Leave to stand for 20 minutes.
Line a dinner plate with baking parchment. Put a 20cm non-stick frying pan over a medium heat, add a little of the oil and swirl around the pan. Pour a ladleful of batter into the pan, swirling so the batter covers the base in a thin layer. Cook the pancake for 30 seconds to 1 minute, then flip it over and cook the other side. Remove from the pan on to the prepared plate.
Repeat with the remaining mixture until you have 8 pancakes, layering with a sheet of baking parchment between each one to prevent sticking.
Melt the chocolate in a bowl over a pan of simmering water, then stir in the raisins and peanuts. Spoon over the pancakes, dust with icing sugar and serve.