Raspberry rosewater cream
1.Preheat oven to 180°C. Grease two 20cm round cake pans; line base and side with three layers of baking paper.
2.Beat butter in a large bowl with an electric mixer until smooth. Add egg whites, extract, sugar, flour and buttermilk.
3.Stir soda and vinegar in a small bowl until foamy; stir in colouring. Add to butter mixture. Beat on low speed until ingredients are combined. Beat on medium speed 2 minutes or until mixture turns a paler colour (mixture may look slightly curdled at this stage). Divide mixture between pans.
4.Bake cakes for 45 minutes or until a skewer inserted into the centre comes out clean. Stand cake in pans for 5 minutes before turning, top-side down, onto wire racks covered with greased baking paper to cool. Split cakes in half horizontally.
5.Make raspberry rosewater cream: Crush raspberries lightly with rosewater in a small bowl. Beat cream and sugar in a small bowl with an electric mixer until firm peaks form. Fold raspberry mixture through cream mixture.
6.Place one cake layer on a plate, spread with one-third of the raspberry rosewater cream, leaving a 1cm border around edge. Repeat layering with remaining cakes and raspberry rosewater cream, finishing with cake.
7.Make rosewater marshmallow: Stir 2/3 cup (150g) of the sugar in a small saucepan with the glucose, the water and rosewater over medium heat without boiling, until sugar dissolves. Bring to the boil; boil 3 minutes or until syrup reaches 115°C on a candy thermometer (or when a small amount of syrup dropped into a cup of cold water can be rolled into a soft ball).
8.Remove pan from heat to allow the bubbles to subside. Meanwhile, beat egg whites in a small bowl of an electric mixer until soft peaks form; beat in remaining sugar until dissolved. With motor operating, add hot syrup in a thin stream, beating on high speed for 5 minutes or until mixture is thick and cooled. Use immediately.
9.Working quickly, use a metal spatula to spread marshmallow over top and side of cake, making peaks and swirls. Serve cake with raspberries.
The cakes can be made a day ahead; store in an airtight container at room temperature. Fill and decorate on the day of serving; keep in a cool place, or refrigerate for up to 3 hours. Stand at room temperature for 1 hour before serving.Note