Preheat the oven to 200C/400F/Gas 6.
For the tarts, cut out the puff pastry to fit six 10cm/4in tart cases. Line the cases with the puff pastry and place into the fridge for 30 minutes to chill.
Prick the base of the pastry in each tart case with a knife, then line with baking paper and baking beans or rice and place onto a baking sheet. Transfer to the oven and bake blind for 15 minutes.
Remove the baking paper and baking beans from the tart cases and return the tarts to the oven to bake for a further 5-8 minutes, until cooked through and golden. Remove from the oven and cool on a wire rack.
Meanwhile, place the pears, lemon zest and juice and sugar into a pan and cover with water. Bring to the boil, then reduce the heat and simmer for 10-12 minutes, or until the pears are cooked and tender. Remove from the heat and allow to cool.
For the cream, place the vanilla seeds and milk into a pan and bring to the boil.
Meanwhile, place the egg yolks, sugar and cornflower into a bowl and mix well.
Once the milk is boiling, pour onto the egg mixture and whisk vigorously. Pour the custard mixture back into the pan and bring back to the boil, stirring constantly.
Once the mixture has reached boiling point, take the pan off the heat and allow to cool.
Meanwhile, pour the pear liqueur into the cream and whip until soft peaks are formed when the whisk is removed.
Fold the cream mixture into the custard gently, so as not to lose too much volume.
Place the apricot jam into a saucepan with a teaspoon of water and warm through.
Fill the cooled pastry cases with the pear liqueur cream.
Place a poached pear half onto a board and cut into slices. Fan the pear slices slightly and gently place onto the cream.
Pour the warm apricot sauce over the pears.
To serve, place each tart onto a dessert plate and garnish with a sprig of mint.