In a medium mixing bowl, whip cream until firm peaks form. Cover and place in the refrigerator.
In a small dish, combine gelatine and 1 1/2 tablespoons boiling water. Set aside after a quick mix to blend.
Allow two pieces of baking paper to overflow the sides of a 5-cup size pudding mould.
In the bowl of a stand mixer fitted with the paddle attachment, beat cream cheese until no lumps left. Scrape down the edges and bottom as needed, and beat in the sugar, vanilla, and mixed spice until well blended. Gradually whip in the gelatine mixture while the mixer is running until it is completely incorporated.
Fold whipped cream into cheese mixture carefully. Combine the crumbled Christmas pudding, pistachios, and chopped cherries in a large mixing bowl. Transfer the mixture to the prepared pudding basin as fast as possible. Refrigerate for six hours or overnight until hard, smoothing the top of the pudding with the back of a spoon.
When ready to serve, turn the pudding onto a serving platter and peel away the baking paper. Drizzle with chocolate sauce that has been gently cooled, then top with crushed pistachios and whole and split cherries.