Step 1
Preheat oven to 170°C. Grease two 22cm round (base measurement) cake pans. Line bases and sides with baking paper. Sift the flour, ginger, cornflour, baking powder, bicarbonate of soda and salt in a large bowl. Stir in the sugar.
Step 2
Combine the milk, sour cream and cordial in a separate bowl. Heat in the microwave on high for 30 secs. Stir well. Gradually whisk into the flour mixture with butter, stirring until just combined.
Step 3
Use an electric mixer to whisk egg whites in a clean, dry bowl until light and fluffy. Fold into the butter mixture, in 2 batches, until just combined. Divide among prepared pans. Bake for 50-55 mins or until a skewer inserted in centre of cakes comes out clean. Cool in the pans for 10 mins before turning onto a wire rack to cool completely.
Step 4
Meanwhile, to make the Swiss meringue buttercream, whisk egg whites and sugar in a heatproof bowl until combined. Place bowl over a saucepan of simmering water. Whisk until mixture reaches 71°C on a sugar thermometer.
Step 5
Use an electric mixer to whisk the egg white mixture until stiff peaks form. Stand for 5 mins or until meringue cools to room temperature. With the mixer on medium speed, add the butter, 1 piece at a time, beating well after each addition. Beat in the vanilla and salt.
Step 6
Use a serrated knife to trim the top of each cake to level. Place a dollop of the buttercream on a plate. Top with 1 cake, cut-side up. Spread with one-third of buttercream and sprinkle with half the crushed biscuits. Place the remaining cake, cut-side down, on top. Use an offset spatula to evenly smooth the buttercream over the top and sides of the cake. Decorate with candy canes and remaining biscuit.