Bring a large pot of lightly salted water to a boil. Cook bow-tie pasta at a boil, stirring occasionally, until tender yet firm to the bite, about 12 minutes.

Meanwhile, heat 1 tablespoon olive oil in a deep, nonstick skillet over medium-high heat. Cook and stir sausage until browned and crumbly, 5 to 7 minutes. Transfer to a paper towel-lined plate. Drain and discard grease.

Heat teaspoon oil in the skillet. Add onion and garlic; saute until tender, 5 to 8 minutes. Drain pasta and return to the pot.

Add wine and sage to the skillet. Simmer until wine is reduced by half, about 2 minutes. Pour in chicken stock and pumpkin; stir until sauce starts to bubble. Return sausage to the skillet. Reduce heat and stir in half-and-half. Season sauce with cinnamon, nutmeg, salt, and pepper. Simmer until sauce thickens, 5 to 10 minutes.

Pour pumpkin cream sauce over the pasta. Toss over low heat for 1 minute. Taste and adjust seasoning.