Warm the custard up, if not freshly made, on low heat. Add 5 drops of the panettone aroma to it and mix it up.
Slice the panettone up thinly and spread each slice with butter.
Arrange the panettone slices in layers, slightly overlapping, butter side up.
Scatter the crumbled Christmas pudding all over.
Spread 2-3 ladles of the warm custard all over this first layer. Depending on the size of your dish and panettone, you'll have about 2-3 layers.
Make another layer up, butter side up, leaving this bare, any topping now would burn.
Ladel about three quarters of the custard onto the panettone, lightly pressing down to encourage absorption.
Leave the whole thing for about half an hour, up to three hours if making ahead. Panettone soaks up a lot of custard, so be over generous!
Preheat oven to 180C/160C Fan.
Top the panettone mix with the rest of the custard and bake in the oven for about 30 minutes. It will look set but will still be wobbly and soft on the inside.
Sprinkle the pudding generously with the sugar and place under a hot grill to to glaze. Don't worry if bits of the panettone get slightly burnt - it adds to the taste!
As mentioned, I use a blowtorch for this - it's more fun!
You shouldn't need any extra custard, as the pudding will be very moist.