You need to begin this by soaking the dried mixed fruit in the rum overnight.
The next day, toast the almonds. To do this, pre-heat the grill to its highest setting for 10 minutes, then place the almonds on some foil and toast them under the grill for 2-3 minutes, but don't go away, as they will burn very quickly.
When they look nicely toasted and browned on one side, turn them all over and toast the other side, then remove them from the grill and leave them aside to cool.
Next, cut the panettone into 1 inch (2.5 cm) chunks and place them in a large mixing bowl, along with the candied peel, orange and lemon zests and the soaked, dried mixed fruit and any drops of rum that didn't get soaked up.
Now chop the almonds into thin slivers and add these. Now give it all a really good stir to distribute everything evenly. Then, in another bowl, whisk together the sugar, milk, cream and eggs and pour this all over the panettone, giving everything another good mix.
Now pour the mixture into the buttered pudding basin and press everything down to pack it in.
Now cover the top of the pudding with a double sheet of foil measuring about 10 inches (25.5 cm) square and tie it securely with the string round the top of the basin, then make a string handle by taking a length of string over the top of the pudding basin and attaching it to each side – this will help you lift the pudding into the steamer.
Now boil a kettle and pour the boiling water into the saucepan, about half full, place it on a medium heat and, when it comes back to the boil, fit the steamer over the top. Now pop the pudding in, put the lid on and steam the pudding for exactly 2 hours.
After 1 hour, check the water level in the saucepan and, if necessary, top it up with boiling water. If you are using a fan steamer, put in enough water to just reach the steamer, and you'll need to top it up 2 or 3 times.
Meanwhile, make the hot punch sauce.
First prepare the orange and lemon zests, and to do this it's best to use a potato peeler and pare off the outer zest, leaving the white pith behind.
What you need is 4 strips of each zest measuring approximately 2 x 1 inch (5 x 2.5 cm). Then, using a sharp knife, cut the strips into very thin, needle-like shreds.
Now pop these into a medium-sized saucepan, along with the sugar and 10 fl oz (275 ml) water, bring everything up to a slow simmer and let it simmer as gently as possible for 15 minutes.
While that is happening, squeeze the juice from the orange and lemon, and in a separate bowl, mix the flour and butter together to form a paste.
When the 15 minutes is up, add the orange and lemon juice, along with the rum, brandy and sherry, and bring it all back up to a gentle heat.
Now add the paste to the liquid in small, peanut-sized pieces, whisking as you add them, until they have dissolved and the sauce has thickened.
Serve the sauce hot in a warmed serving jug, and if you make it in advance, re-heat it gently without letting it come to the boil.
To serve the pudding, remove the foil and string and let it stand for 5-10 minutes, then slide a palette knife all round to loosen it and turn it out on to a warmed plate.
Pour some of the hot punch sauce over the pudding and carry it to the table, with the rest of the sauce in a jug to hand round separately.