Cream the butter and sugar until pale and soft.
Add in the vanilla paste or extract and the eggs one at a time, mixing well after each egg.
Sieve in the plain and rice flour, cocoa powder, baking powder and salt and mix with a fork until it forms a rough ball of dough.
Knead the dough a little on a lightly floured work surface, before wrapping in clingfilm and resting in the fridge for 40 mins.
Preheat the oven to 160C and line a baking tray with greaseproof for the biscuits and get a muffin tray ready for the nests.
Divide the dough in half, dust a little flour onto a work surface and roll out the dough to the thickness of a pound coin.
Cut out rounds of the dough to fit your muffin tin and press the dough gently into the holes.
For the biscuits, cut out rounds measuring 4cm and place on the lined baking tray.
Continue rolling and cutting, gathering off-cuts, until all the dough has been used.
Prick the biscuits and nests with a fork to stop them puffing up in the oven, then bake for 12 mins.
Leave to cool on a baking tray before filling and decorating.
While the biscuits are cooling, make the buttercream by mixing all the ingredients together to form a smooth paste – it’s important that your butter is soft.
Spoon 1 tsp buttercream into the nests and decorate with mini chocolate eggs.
For the biscuits, spread 1 tsp buttercream onto one biscuit and sandwich together with another biscuit to complete your classic bourbon biscuit.