1. Cook pasta according to package directions; drain. Keep warm.
2. Meanwhile trim fat from beef steak. Cut steak lengthwise inhalf and then crosswise into 1/8-inch thick strips. In wok or large skillet, heat 1 to 2 tablespoons oil over medium-high heat until hot. Add beef and garlic, 1/2 at a time, and stir-fry 1 to 2 minutes or until outside surface is no longer pink. Remove from pan with slotted spoon; season with salt and pepper. Keep warm.
3. In same pan, heat 1 tablespoon oil until hot. Add mushrooms and bell pepper strips; stir-fry 3 to 4 minutes or until mushrooms are tender. Remove from heat. Return from heat. Return beef to pan; add sliced basil and toss.
4. Place pasta on large deep oval platter; arrange beef mixture on pasta. Sprinkle cheese over beef and pasta or pass separately, if desired. Garnish with basil sprigs and bell pepper rings.
Cook's Tip: Your favorite mushroom may be substituted for portabella.