To make the filling, melt chocolate and butter in a microwave on 50% power in 20 second bursts, until melted. Add sugar and cocoa and stir until smooth. Place in fridge to cool and thicken. Divide in half and reserve one half for decorating.
Whisk half of the filling in a freestanding mixer until thick and fluffy. Place in a piping bag with star nozzle and set aside in fridge.
Preheat oven to 175°C fan forced and line a baking sheet with baking paper.
Lay one and a half pastry sheets on bench and spread over remaining chocolate filling evenly to the edges.
Place remaining pastry on top to cover. Brush with milk. Cut pastry into 18 strips.
Twist the strips and then roll the twists into a spiral. Place the pastry spirals on the baking tray. Scatter over sugar. Repeat with remaining pastry, allowing plenty of room to spread.
Bake for 10-12 minutes until pastry is golden and cooked. Remove from oven and cool on wire rack.
Pipe swirls of ganache onto pastry nests and top with mini eggs.