Heat oven to 180C/160C fan/gas 4. Butter and line three 18cm (or two 20cm) cake tins. Beat the butter and sugar together until light and fluffy. Add the eggs, beating them in one at a time. Fold in the flour, baking powder and a pinch of salt, then fold in the crème fraîche and chocolate and 100ml boiling water.
Divide the cake mixture between the tins and level the tops of the batter. Bake for 25-30 mins or until a skewer inserted into the middle comes out clean. Leave to cool for 10 mins in the tin, then tip out onto a cooling rack and peel off the parchment. Set aside to cool completely.
To make the angel frosting, put the sugar, vanilla and liquid glucose in a pan with 125ml water. Bring to the boil and cook until the sugar has melted – the syrup turns clear and the mixture hits 130C on a sugar thermometer (be very careful with hot sugar). Take off the heat. Meanwhile, beat the egg whites until stiff then, while still beating, gradually pour in the hot sugar syrup in a steady stream. Keep beating until the mixture is fluffy and thick enough to spread – this might take a few mins as the mixture cools. Beat in the icing sugar.
Spread two of the sponges with jam and some of the icing mixture, then sandwich the cakes together with the plain one on top. Use a little of the frosting to ice the whole cake (don’t worry about crumbs at this stage). Use the remaining icing to ice the cake again, smoothing the side, and swirling it on top. Crush four of the candy canes and sprinkle over the cake, then add the remaining whole candy canes, meringues and sweets.