Line 5 small rum baba cases with clingfilm, smoothing out as much as possible, and fold the excess over the sides. The clingfilm makes it easier to turn out the jellies, but if you find it fiddly to use, you can dip the rum baba cases in warm/ hot water for 10 seconds when the jellies are ready to serve.
Mix the fruits and divide between the cases. Sprinkle the gelatine into the hot water and leave to dissolve for 4 minutes. For a meat-free alternative such as agar sugar, follow pack instructions for use. Mix to check it has dissolved, add the champagne or sparkling wine and sugar. Stir well.
Pour into the cases and carefully transfer to the fridge to set for 2 hours.
Turn out by placing a plate on top and inverting. Lift off the cases, then peel away the clingfilm (if used) and serve.