Cook the sausage links according to package instructions, allow to cool, then slice into ½ inch slices.
While the sausage is cooking, bring the heavy cream and ground fennel to a boil in a heavy-bottomed pot, then remove from the heat.
Stir in pumpkin puree to the fennel cream and reserve.
Heat a heavy-bottomed skillet over medium-high heat, add the olive oil and onions and cook, stirring frequently, until caramelized, reserve.
Stretch the dough balls into 2 large, greased pizza pans.
Spread the pumpkin cream over the crusts, top evenly with the sliced brats, then onions, then sage, then Parmesan cheese.
Bake for approximately 15 minutes, or until browned and bubbly.
Rest the pizzas for 3 minutes, then cut as desired.