Preheat the oven to 160C/fan 140C/gas 3. Grease two 450g loaf tins (top measurement 17cm x 11cm) and line with baking parchment.
Mix the muscovado sugar with the butter and the eggs in a mixer until light and fluffy and the fold in the flour, mincemeat, currants and sultanas.
Split the mixture between the prepared loaf tins and arrange the nuts on top and then sprinkle with the demerara sugar.
Bake in the preheated oven for about 1¼ hours or until the cakes are golden brown, firm to the touch and a skewer inserted into the centre comes out clean.
Allow the cakes to cool in the tins for a few minutes, then loosen the sides with a small palette knife, turn out on to a wire rack and leave to cool.