Preheat the oven to 200°C. Line a baking sheet with a silpat mat or parchment paper.
Add the hazelnuts to a large soup pot over medium heat and cook, stirring frequently, until fragrant, about four to five minutes. Remove the hazelnuts to a small bowl and reserve the pot.
For the hazelnut frico: Sprinkle the cheese into eight thin rounds, about 5cm wide on the prepared baking sheet. Finely grind the toasted hazelnuts in a food processor, and evenly sprinkle over cheese rounds. Evenly drizzle the rounds with a small amount of olive oil. Bake until golden brown and bubbly, about five to six minutes. Remove from the oven and set aside.
Add the butter to the pot the hazelnuts were toasted in over medium heat, and cook, whisking frequently, until the butter starts to brown and foam, about two to three minutes. Stir in the onion, carrot, celery, sage, cinnamon, ginger and nutmeg, and cook until tender, stirring frequently, until tender. Stir in the garlic and cook an additional minute.
Stir together the half-and-half and cornstarch in a liquid measuring cup, and pour it into the pot, along with the chicken broth, pumpkin puree, brown sugar, salt and pepper. Bring to a boil over medium-low heat, stirring frequently. When the soup starts to thicken reduce the heat to low. Using an immersion blender, puree the soup until a smooth consistency is reached and simmer until ready to serve. Ladle the soup into serving bowls and float a frico over the top.
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