Cook tortellini in pot of boiling salted water until just tender but still firm to bite. Drain, reserving 1 cup cooking liquid. Sauté bacon in large skillet over medium-high heat until crisp and brown. Using slotted spoon, transfer bacon to paper towels to drain. Pour off all but 3 tablespoons drippings from skillet. Add mushrooms, onions, garlic, and sage to skillet. Sauté over medium-high heat until mushrooms are tender, about 8 minutes. Add 1/2 cup reserved pasta cooking liquid to skillet. Bring to boil over medium-high heat. Whisk egg yolks and cream in small bowl to blend. Add cream mixture, tortellini, and 1/3 cup Parmesan cheese to mushroom mixture. Toss until sauce thickens and coats tortellini, adding more cooking liquid by tablespoonfuls to thin sauce, if desired, about 3 minutes. Season with salt and pepper. Transfer pasta to serving bowl and sprinkle with remaining 1/3 cup Parmesan cheese.
