Preheat oven to 450 F. Place sweet potato cubes on a baking sheet, sprinkle with chili powder, cinnamon, ginger, and sugar, then drizzle with olive oil. Toss to coat, then roast in oven for 20 minutes or until tender.
Meanwhile, cook pasta according to package directions. Drain, reserving hot pasta water.
In a large skillet, sauté onion whites and pancetta over medium heat until pancetta is almost crisp. Add minced garlic and cook another minute or so. Lower heat.
Add peanut butter, cream cheese, chili sauce, and soy sauce. Slowly stir in 1 cup pasta water, continuing to stir until smooth and creamy. If sauce is too thick, whisk in additional water a few tablespoons at a time.
Add black pepper and sage.
Plate pasta, top with sauce and sweet potatoes, and sprinkle with diced green onion.
Per serving: 717 calories, 31 grams fat (11 grams saturated fat), 86 grams total carbohydrates, 9 grams fiber, 25 grams protein.
