Break the chocolate into chunks and add to a microwave proof bowl. Add the oil and then heat on high, stirring every 30 seconds, until fully melted. Set this bowl to one side to cool.

In a large mixing bowl, whisk the egg yolks and sugar until fluffy. Pour the chocolate mixture into the egg yolks and whisk. Then whisk the flour into the chocolate batter.

In a separate mixing bowl, whisk the egg whites into stiff peaks. Then fold the egg whites into the chocolate batter. Stir with a metal spoon until the whites have been incorporated, but try not to knock the air out.

Pour the batter into the prepared baking tin. Bake in the centre of the oven for 40 minutes or until a skewer inserted into the cake comes out clean. Allow the cake to cool for ten minutes in the tin, then remove and allow to cool completely on a wire rack.

Break 100g of chocolate into chunks and place in a small microwave-proof bowl. Heat on high for approximately 2 minutes, stirring every 30 seconds until melted. Pour over the cake and decorate with mini eggs.