Preheat the oven to 375°F (190°C) for gentle caramelization, or 400°F (200°C) for deeper color and a more intense crust.
Prep the pear. Halve the pear lengthways and use a melon baller to scoop out the seeds and core, creating a neat cavity.
Make the glaze. In a small bowl, mix together the butter, maple syrup, brown sugar, cinnamon, and a few drops of vanilla extract until combined.
Roast. Place the pear halves cut-side up in a baking dish. Spoon the glaze generously over each half. Roast for 35–40 minutes until completely soft and deeply caramelized at the edges.
Make the ganache (start this while the pear roasts). Heat the heavy cream in a small saucepan until just steaming - do not boil. Pour over the chopped chocolate in a heatproof bowl. Leave untouched for 1 full minute, then stir slowly from the center outward until completely smooth. Add the pinch of flaky salt and stir to combine. Refrigerate for 20–30 minutes until thick and spoonable.
Temper the ganache. About 5 minutes before the pears are done, remove the ganache from the fridge. It should be thick and spoonable - not liquid, not set hard.
Rest the pears. Remove from the oven and rest for 3–5 minutes. If liquid has pooled in the cavity, tip each half briefly cut-side down onto a paper towel before plating.
Assemble. Place pear halves cut-side up on serving plates. Spoon ganache into the center of each and allow it to settle naturally. Finish with chopped toasted hazelnuts and serve immediately.