Prepare the Bosc pears by peeling the skin and slicing them in half. Discard the core by scooping it out or using a pairing knife. Cut out and discard the stem lines that run from the stem to the core. Then, cut off the end.
In a medium-large skillet that’s oven safe (mines is 10 inches in diameter), melt the unsalted butter over medium heat. Once the butter has melted, add in the sugar and stir to create a sandy mixture.
Distribute the sliced pears around the pan (with the insides facing up). For the center of the skillet, place the bottom half of a pear to form a flower shape. You might have to move the pears around to make them fit in the skillet.
Allow the pears to sit in the mixture over medium heat without moving them, for the sugar to caramelize (this should take around 10-15 minutes). Keep a close eye so that it doesn’t burn. It’s ready once the bottom of the pears turn golden brown. Cool completely.
Preheat the oven to 425°F.
Sprinkle the cinnamon and ginger over the pears and also in between them.
On a lightly floured surface, roll out the puff pastry to a large circular shape that has a diameter of 12 inches, and a thickness of 2mm. Place over the skillet and tuck in the edges around the pears.
Bake in the oven for 30-35 minutes, until the top of the pastry is a deep golden brown color. Then, let cool for 5 minutes to allow the caramel to stop bubbling.
Cover the skillet with a plate that’s larger than the skillet, and be brave and flip it over. Let cool for 10 minutes, and serve. Slice and enjoy!