Preheat the oven to 180 degrees C/ 350 degrees F/ Gas 4. Lay out 6 sheets of filo pastry on a clean tea towel, overlapping each by an inch or so, so they cover the tea towel.
Cook's Note: The filo should cover the tea towel completely, with just a little overhang at one of the shorter ends.
Work quickly so your pastry doesn't dry out and brush some melted butter all over it. Sprinkle over the cinnamon and 2 ounces/ 50 g of the sugar, then crumble over your ginger nuts to add a nice bit of crunch. Carefully layer the rest of the pastry sheets on top and brush again with butter.
Use your hands to crumble the Christmas pudding into a bowl then grate in the fruit, cores and all. You want to have about the same amount of grated fruit as you've got pudding. Add about 2 tablespoons of sugar, and mix it all together to break up the pudding a bit more. Sprinkle this all over the pastry so it's roughly covered, leaving the overhang clear. Place the chocolate in a row on top of the Christmas pudding, down the short side nearest the overhang.
Fold the overhang over the chocolate and pinch it up, then lift up your tea towel, and use it to help you carefully roll up your strudel. Tuck the ends under to seal it and transfer to a large nonstick pan. Brush it all over with butter then sprinkle over a little more sugar. Bake in the hot oven for about 40 minutes until crisp, golden and gorgeous looking. It might split a bit and look slightly rustic, but I think that's quite nice. Cook's Note: You could wrap an extra layer of filo round it before cooking if you want it to look a bit neater.
Once the strudel is cooked, leave to cool, then use a serrated knife to cut the strudel into
2-inch/ 5 cm slices. Dust these with icing sugar and serve with ready-made custard from the refrigerator.