Place the panettone in the bottom of 4 glass serving dishes.
Put the raisins, half of the cinnamon and 100 ml (3 1/2 fl oz) of the juice from the pears in a saucepan over a medium-high heat and bring up to a gentle boil. Reduce the heat and simmer for a minute, then turn off the heat and set aside for 5 minutes.
Meanwhile, heat a frying pan over a medium heat, put the hazelnuts in the pan and dry-roast until golden. Remove from the pan and crush lightly.
Beat the custard with the remaining 1/2 teaspoon cinnamon in a bowl and slice the pears into thick pieces.
Pour the warm raisin mixture over the panettone cubes and cover with the sliced pears. Pour over the custard and place in the refrigerator for 8–10 minutes.
Spoon 1 tablespoon of the crème fraîche over each trifle and serve scattered with the crushed toasted hazelnuts.