Melt the butter in a large pan over medium heat. Add the flour, and whisk to fully mix. Add the garlic, and continue to whisk until the garlic has turned fragrant and the flour as just started to turn golden brown. Add the milk in 1/2 cup portions at a time, whisking completely before adding the next amount. Add the milk until a cream sauce has formed, but not too thin. Cook until the sauce is thick enough to stick to the back of a wooden spoon. Whisk in the pumpkin, nutmeg and cinnamon, and salt and pepper to taste. Add the cream cheese and parmesan and stir until cheeses are completely melted and mixed into the sauce. Set a pot of heavily salted water to boiling. Cook the macaroni according to instructions. Drain the macaroni, then add to the pan with the sauce and mix well. Transfer to serving dish and sprinkle with hazelnuts. Serve.