To make the biscuits:

Preheat the oven to 180°C/160°C Fan/Gas Mark 4.

Rub the butter into the flour and stir in the sugar. Add the eggs and knead the mixture together to form a dough. Place into the refrigerator for at least 2 hours.

Roll out the dough to 3mm thickness and cut shapes out of the dough with a cookie cutter of your choice. Be sure to make an even number of biscuits.

Place the shapes on the baking tray and bake for 15 minutes until golden brown. Remove onto a wire rack to cool.

To make the buttercream:

Whisk the eggs and sugar in a bowl over a pan of simmering water until thickened, remove from the heat and allow to cool.

In a separate bowl beat the butter until creamy, then add the egg mixture gradually, beating continuously until well mixed.

Pipe the buttercream onto a biscuit using a piping bag, and sandwich together with a second biscuit. Continue with the remaining biscuits.

To finish:

Melt the chocolate together with the oil in a bain-marie. Dip a third of each biscuit into the chocolate and allow to set.