Method

1. Preheat the oven to 160°C. Line a large baking tray with baking paper. Grease three 5-inch cake rings and place on the prepared tray.
2. Weigh out three 250g balls of cookie dough. Press into each of the prepared cake rings to create an even layer. Bake for 25 minutes until golden, then remove from the oven and cool completely, then remove from the cake rings. Save the leftover cookie dough to make cookies for later.
3. Meanwhile, make the topping. For the buttercream, place egg whites and sugar in a large bowl set over a saucepan of simmering water. Whisk until the egg whites reach 70°C, then remove from the heat and whisk for 10-15 minutes until stiff peaks form. Gradually add the cold butter, whisking until combined. Fold through the sprinkles until combined.
4. To assemble, line one of the cake rings with a 60cm-long, 15cm-tall piece of acetate. Place one cookie cake in the base of the cake ring, then top with 250g buttercream. Repeat layering with cookie cakes and buttercream, finishing with a buttercream layer. Transfer remaining buttercream into a piping bag and pipe on top of the finished cake. Top with fairy bread pieces, to serve.