Place the flour and sugar in a bowl and mix until all combined. Add the butter to the bowl and rub into the dry ingredients until they form a breadcrumb consistency.
Add the egg yolk and stir through so the mixture begins to clump together. Add the milk (you might not need to add all the milk) and using your fingers begin to bring pastry dough together. Pour the pastry dough onto a lightly floured surface and knead lightly to form a smooth dough.
Roll the pastry out onto a lightly floured surface to a thickness approx. 1/2cm. Using a round cutter slightly larger than your tartlet tins cut 4 circles out of the pastry, re-rolling as necessary. Place the circles of pastry in the tartlet tins and press into place. Wrap the left over pastry in cling film and place in the fridge, you will need this for the pie topping.
Prick the base of the pastry case with a fork a couple of times and place a square of greaseproof paper over each pastry case and fill with baking beans. Place the pastry cases in the fridge to chill for 30 minutes. 10 minutes before baking, pre-heat the oven to 200°C (180°C Fan/Gas Mark 6).
Once chilled place the pastry in the centre of the oven the blind bake for 20 minutes. Once baked remove from the oven and remove the baking parchment and baking beans and place the pastry cases back in the oven for a further 5-7 minutes to allow the pastry base to firm up. Once baked remove from the oven and leave the pastry cases in their tins to cool.
Once the pastry cases are cooled make the filling; firstly poach the pears. Place the thinly sliced pears into a saucepan add the golden caster sugar, cinnamon and 100ml water. Scrape the vanilla seeds out of the vanilla pod and add the seeds and pod to the pan. Gently heat the pear mixture stirring to dissolve the sugar. Cover the pan with a lid and leave the mixture to simmer for 15 mins until the pears have softened and remove from the heat.
Divide the poached pears between the pastry cases. Sprinkle the hazelnuts and Chocolate Chips over the top of the pears and pour over some of the poach pear liquid.
Re-roll your left over pastry to a thickness of approx. ½ cm. Cut the pastry into thin strips, this will create the lattice topping. Ensuring the strips are long enough then fit across the top of the pie, cut 24 strips of pastry.
Whisk the egg into a small bowl. Brush the egg around the edge of the pastry cases to allow the pastry strips to stick. Place 6 strips of pastry onto each pie, 3 strips vertically and 3 strips horizontally ensuring they are evenly spaced apart. Create the lattice effect by placing the strips of pastry over and under each other alternating. Gently press the edge of the pastry strips onto the pastry case, cutting away any excess. Brush the pastry lattice with the egg glaze and sprinkle with sugar.
Place the pies back in the oven and bake for 20-25 mins until the pastry is golden brown and the filling is bubbling.
Your pies are best served fresh from the oven with a dollop of ice-cream.