In a medium saucepan cook butternut squash, covered, in a small amount of boiling salted water for 10 minutes or until tender; drain and set aside.
In a very large skillet cook turkey kielbasa in 1 tablespoon hot oil over medium heat until lightly browned and crisp on the edges. Add butternut squash, yellow sweet pepper, sage, vinegar, and sugar; bring to boiling. Reduce heat; simmer, uncovered, until vinegar has almost evaporated. Remove from skillet. Cover with foil to keep warm.
Rinse and wipe out skillet. Add remaining 1 tablespoon oil. Fry polenta slices in hot oil over medium-high heat until golden brown, about 5 minutes. Turn with pancake turner; fry 5 minutes more. Stack three polenta slices on each of four dinner plates. Top with sausage mixture; drizzle each serving with maple syrup. Makes 4 servings.