Scoop steamed flesh of squash into a mixing bowl and discard the peel.
Add parmesan, thyme and garlic to the mixing bowl and stir together until well combined. Season with salt and pepper.
Place 3 pasta sheets or ½ the wonton wrappers onto a lightly floured surface and drop 1 ½ tablespoons of the filling mixture onto the surface of the pasta, 2 inches apart. (if using wonton wrappers, place a dollop of filling onto each wrapper)
Brush a small amount of the egg wash over the surface or the pasta or wonton wrapper and place an unused sheet of pasta/wrapper over the top and gently press around the filling to remove any air and seal the sheets/wrapper together.
Cut the raviolis using a 2½-3 inch circle cutter and place onto a baking sheet, discarding all the scraps.
Bring a large pot of water up to a boil and season well with salt. Carefully drop the raviolis into the water one at a time and stir. Allow the raviolis to boil for 5 to 7 minutes and drain.
Drizzle raviolis with a small amount of olive oil, to prevent them from sticking, and set aside.
For the sauce: Melt butter in a small saucepan over medium-high heat. Sauté shallot and garlic for 3 to 4 minutes. Add thyme sprigs and continue to sauté for an additional minute.
Deglaze with the wine and allow the mixture to simmer until the pan is almost dry. Add cream and ½ the hazelnuts and simmer for 5 to 6 minutes or until the cream has reduced by ½. Season with salt and pepper.
Strain the sauce and stir in the remaining hazelnuts. Place the ravioli onto a platter or individual plates and drizzle with the cream sauce. Garnish with fried sage leaves, if using, and serve warm.