Whisk egg yolks and 100g sugar in a bowl until combined.
Heat milk and 300ml cream until boiling, then whisk into egg yolks and thicken over heat.
Sieve custard over white chocolate, stir until melted, cool, and churn in ice cream machine.
Rub 250g butter into flour and salt, then mix with 125ml cold water to form dough.
Form dough into a rectangle, wrap, and refrigerate for 20 minutes.
Roll dough to 40x20cm, fold in thirds twice with chilling intervals, and refrigerate for 30 minutes.
Preheat oven to 200°C.
Simmer pears with lemon zest, vanilla, cinnamon, orange peel, and 25g sugar for 15 minutes.
Melt 85g sugar into caramel in a 24cm pan, stir in 110g butter, 150ml cream, and vanilla pods.
Roll pastry to 5mm thickness and cut a circle larger than the pan.
Place pastry over pears in the pan and bake for 20-25 minutes.
Dissolve 75g sugar in 110ml simmering water, then whisk in dark chocolate until smooth.
Invert the tart onto a plate and serve with ice cream and chocolate sauce.