Orange chiffon cake

Preheat oven to 180°C/160°C fan forced. Put a baking tray in oven to preheat. Triple-sift flour into a bowl. 

Using an electric mixer, beat egg yolks and sugar in a medium bowl for 5 minutes or until thick and pale.

 Using a whisk, combine orange juice, oil and orange zest in a small bowl. Gradually add orange juice mixture to egg yolk mixture, beating until combined. Sift flour over mixture and gently fold to combine. Set aside. 

Using a clean electric mixer fitted with a whisk attachment, beat egg whites in a bowl until foamy. Add cream of tartar, then gradually add extra sugar, beating until mixture is thick and glossy. 

In 3 batches, fold egg white mixture into cake mixture until just combined. Spoon into an ungreased 25cm angel food cake pan with a removable base and smooth surface.

Put cake pan on preheated oven tray. Bake for 55 minutes-1 hour or until a skewer inserted into centre comes out clean. Put a piece of baking paper, just larger than the pan, on a work surface. Immediately turn hot pan upside-down on paper and leave to cool completely in this position.

Carefully run a small knife around edge of cake and tube to help release cake from pan (you may also need to run a knife or spatula between base and cake). Using a sharp knife, cut cake into three even layers. 

For filling, using an electric mixer fitted with a whisk attachment, whisk cream, sour cream, icing sugar and vanilla until stiff peaks form. Put 1 cake layer on a cake stand. Spread with 11/4 cups filling. Repeat layering with cake and filling until all cake layers have been used, finishing with cake. Spread remaining filling over top and sides. Refrigerate for 30 minutes or until firm. Decorate with edible flowers to serve.