Preheat the oven to 200C/400F/Gas 6.
To make the pastry, mix the flour and butter in a food processor until the mixture starts to resemble coarse breadcrumbs.
Add the egg yolk and enough water for the pastry to bind.
Bring the pastry together and, on a floured surface, roll the dough to a ½cm/¼in thickness. Cut out two large pear shapes, then place on a baking tray and bake for 10 minutes.
For the pear, bring the wine, water, sugar and bay leaf to a simmer in a small saucepan. Poach the pear halves in the syrup for 10 minutes, weighed down with a small plate to submerge the pear.
To make the filling, mix together the goats' cheese, chives and chopped salad onion, then season with salt and freshly ground black pepper.
Stuff this mixture into the cored poached pear halves and place the pears on the pastry. Bake in the oven for 10 minutes.
Serve on a large warm plate and garnish with the basil leaf.