Place the currants, raisins and sultanas in the bowl and pour the sherry over, using the K beater, mix on speed 1 for 45-60 secs. When mixed, set aside in a glass bowl, cover with cling film and leave to soak for at least 2 hours.
Still using the K beater, beat together the butter and brown sugar on speed 2 for 2 minutes, until creamed together. Beat in the eggs, pouring in slowly while mixing on speed 2 for another minute, then fold in the flour on speed 1 for another minute. Pour in the soaked fruit and sherry with the breadcrumbs, almonds, orange juice and rind, lemon rind, and mixed spice, mix on speed 2 for a minute.
Grease a 1.2 litre (2-pint) pudding basin and spoon the mixture into it, packing it down well and leaving a gap of approx. 2.5cm at the top. Cut a round of greaseproof paper 3cm larger than the top of the basin, grease with butter and place over the pudding. Secure with string, then top with 2 layers of foil.
Place the pudding in a saucepan filled with boiling water that reaches two thirds of the way up the basin. Reduce the heat and simmer for 6 hours, topping up the water in the saucepan when necessary.
Remove from the heat and leave to cool. Renew the greaseproof paper and foil and store in the refrigerator for 2-8 weeks. To re-heat steam as before for 2 hours, decorate with holly, a dusting of icing sugar and serve.