Preheat oven to 160⁰C. Grease and baking paper-line a 22cm cake tin.
For jelly, soak the gelatine in cold water for 5 minutes or until softened.
Pour champagne and sugar into a saucepan and bring to a boil. Boil for a few minutes to boil off some of the alcohol. Remove from heat and allow to cool slightly. Drain gelatin and squeeze out excess water, add to saucepan and stir until gelatine dissolves. Cool to room temperature.
Pour jelly into the trifle bowl and add raspberries. Refrigerate until set.
For almond cake, whisk egg whites to firm peaks and gradually beat in butter. Sift almond meal, castor sugar and salt into egg whites and gently fold with a metal spoon to incorporate.
Spoon into prepared cake tin and bake for 45-50 minutes or until an inserted skewer comes out clean.
For rhubarb, place rhubarb in a bowl, cover with sugar and gin and allow to soak, covered with cling wrap, for 12 hours in the refrigerator.
Pour rhubarb mixture into a greased baking tray and bake for 20 minutes or until soft.
For mascarpone cream, place mascarpone in a large bowl of an electric mixer with cream, vanilla and sugar and beat until smooth. Refrigerate, covered until required.
Once the jelly is set in the trifle bowl, slice cake in half horizontally so you have two thinner cakes. Place the top layer of cake on top of the jelly and spoon over a thick layer of rhubarb. Fill the rest of the bowl with mascarpone cream mix. Place in the fridge for a good 2 hours to set and hold.
To serve, arrange raspberries on top and decorate with shaved chocolate.