Preheat oven to 350 degrees.

Bring a large pot of salted water to a boil and prepare pasta according to directions, cooking for 1 to 2 minutes less than directed. Drain and set aside.

In a large saucepan over medium heat, melt butter. Once sizzling whisk in butter to create a roux. Cook, stirring constantly, until golden, approximately 4 to 5 minutes. Stir in garlic and cook for 30 seconds. Stir in milk and increase heat slightly until the mixture is bubbling and thickened, approximately 5 minutes. Stir in mascarpone, parmesan, pumpkin, sage, salt, pepper and pumpkin pie spice, mixing well until the cheese is melted and the sauce is thick and smooth.

Grease a baking dish with nonstick spray and add pasta. Pour sauce over the top and toss well to coat. Grate some fontina over the top and sprinkle over some breadcrumbs.

Bake for 15 to 20 minutes, until golden and bubbling. Serve immediately with sage leaves for garnish.