The fragrance of the rose water and richness of the pistachio marzipan makes this a truly festive treat. Serve it simply: dusted with icing sugar.
Make the dough. Place the dried fruit into a small bowl with the clementine zest, 4 tablespoons of the juice, and the rum. Leave for 30 minutes for the fruit to soak.
Mix together the flour, yeast, salt, cinnamon, cloves and sugar in the bowl of a stand mixer fitted with the dough hook.
Stir the milk into the melted butter, then beat in the eggs. Pour the wet ingredients into the flour mixture and add the soaked fruit along with the soaking liquid. Mix for 5 minutes to form a soft dough, then cover the bowl with cling film and set aside to rise for 40 minutes to 1 hour, or until doubled in size.
Meanwhile, make the marzipan. Place the pistachios in a food processor and blend until very finely chopped, then add the icing sugar, egg yolk and rose water, blend for a few seconds, then add 2–3 teaspoons of egg white to form a crumbly ball. Use your hands to bring the mixture to a soft paste, adding a little extra egg white if needed. Wrap the marzipan tightly in cling film and set aside until needed.
Once the stollen dough has risen, divide the marzipan into 2 balls and roll each ball into a rectangle measuring about 40 x 12cm. Divide the stollen dough in half and roll each half into a rectangle about 45 x 16cm. Lay a marzipan rectangle over each piece of dough, then roll up each from the long edge into two long Swiss rolls.
Pinch together the edge of each roll to seal, then use your hands to roll them into ropes measuring 56cm long and of even thickness throughout. Twist the 2 ropes together and form into a circle. Pinch the ends together, then place the circle on a lined baking tray. Cover with a large plastic bag and leave to prove for 40 minutes, or until almost doubled in size.
Heat the oven to 180°C/160°C fan/350°F/Gas 4, then bake for 45–50 minutes until golden brown and risen. Remove from the oven and brush immediately with extra melted butter.
Reserve 200g of icing sugar for the drizzle. Put the egg white in the bowl of a stand mixer fitted with the whisk and whisk for 10–20 seconds on medium speed. Turn off the mixer, add some of the remaining icing sugar and whisk on a slow speed. Gradually add the remaining icing sugar, increasing the motor speed as the icing sugar is incorporated.
Use a spatula to wipe any mixture from the sides of the bowl and add the lemon juice. Keep beating at high speed until the icing reaches a piping consistency. Place half the icing in another small bowl and add red food colouring until you reach the desired shade.
Place each icing in a piping bag fitted with a No.3 nozzle, then pipe leaf shapes on the remaining lined baking tray. Dry the leaves in a proving drawer or an oven set at 100°C/80°C fan/200°F/Gas ½ for 10 minutes.
Mix the reserved 200g of icing sugar with about 1 tablespoon of clementine juice to make a thin icing. Use this to stick the leaves to the top.