Preheat oven to 350 degrees F. In a large saucepan cook tortellini according to package directions, adding haricots verts for the last 4 minutes of cooking. Drain and return to pan.
Meanwhile, in a large skillet cook mushrooms and onion in hot oil over medium heat for 6 to 8 minutes or until tender and lightly browned, stirring occasionally.
Add mushroom mixture and chicken to drained pasta mixture. Toss to coat. Place undrained peppers in a blender. Cover and blend until smooth. Stir in pesto and crushed red pepper. Add to pasta mixture;toss to coat. Spread mixture evenly in a 3-quart rectangular baking dish.
Cover and bake for 20 minutes. Uncover and sprinkle with cheese. Bake, uncovered, for 5 minutes more or until cheese is melted.
To tote, cover casserole and place in an insulated casserole carrier. Place basil in an airtight container. Just before serving, sprinkle basil over casserole. Cover and chill leftovers within 2 hours.