Mix the raisins, glacé cherries, cranberries, dark rum, orange juice, zest and nutmeg in a bowl. Cover with cling film and leave the fruit to soak.
Meanwhile melt the vegan butter in a small saucepan. Remove from the heat and stir in the oat milk. Leave to cool for 5 minutes.
Add the flour, sugar, yeast, spices and salt to a mixing bowl. Stir to combine then pour in the lukewarm milk and butter liquid. Stir until the mixture forms a moist, slightly shaggy dough. Tip out onto a well floured surface and knead the dough for 6-8 minutes. The dough is ready when it is smooth and springy to the touch.
Form the dough into a ball and transfer to a lightly oiled large bowl. Cover with cling film and leave the dough to prove for 1.5-2 hours. The dough should have risen but not quite doubled in size.
Grease and line a 20cm / 8 inch square baking tin with baking parchment. Sprinkle the icing sugar onto the work surface. Roll out the marzipan to approximately a 20.5cm/ 8inch square and leave to one side.
Next tip out the dough onto a well floured work surface. Pour over the soaked fruit and knead into the dough. Cut the dough in half. Scatter over more flour to help you roll one piece of dough to roughly a 20.5cm/ 8inch square. Place into the prepared tin. Top with the marzipan. Then roll out the second piece of dough, again to approx 20.5cm/ 8 inch and place on top of the marizipan. Cover with cling film and leave to prove for 1 hour.
Pre heat the oven to 180°C / 160°C fan / gas mark 4. Bake the dough for 20-25 minutes, until well risen and golden. Cool for 15 minutes in the tin. Then turn out onto a wire rack and leave to cool completely.
Neaten the bread by trimming the edges. Melt the remaining butter and brush over the stollen. Sprinkle generously with icing sugar then cut into 25 squares.