In a large skillet, melt butter over medium heat. Add pears and sprinkle with sugar. Cook without stirring 2-3 minutes or until underside is golden and caramelized, flip each slice over. Cook other side until golden and browning. Season with freshly ground black pepper and keep warm.
In another skillet, melt remaining butter with the clove garlic for 1 minute until fragrant. Add half hazelnuts and half thyme leaves and toss for 2 minutes.
In the meantime, cook the Tortelloni according to package instructions and drain, reserving a little of the pasta cooking water. Add Tortelloni and caramelized pears to the skillet and toss gently to combine, adding a few spoons of the cooking water to loosen the sauce if needed.
Divide Tortelloni among plates, sprinkle with remaining hazelnuts and thyme. Season with more black pepper to taste and serve.