Heat oven to 350°F. Sprinkle 5-spice powder evenly over all sides of tenderloin. Heat 2 teaspoons of the oil in a large deep skillet over medium heat until hot. Add tenderloin; lightly brown 2 minutes per side. Transfer tenderloin to a shallow baking sheet; bake until internal temperature of tenderloin reaches 165°F, about 20 to 22 minutes.
Meanwhile, heat remaining 2 teaspoons oil in same skillet over medium-high heat. Add rapini; stir-fry 2 minutes. Add bell pepper and mushrooms; stir-fry 3 minutes. Add garlic and pepper flakes; stir-fry 2 minutes or until vegetables are crisp-tender. Add miso paste and broth; cook 2 minutes or until sauce thickens. Remove from heat; stir in green onions.
Transfer vegetables to four serving plates. Slice tenderloin crosswise into ½-inch thick slices; arrange over vegetables. Drizzle any pan juices from baking sheet over turkey.
2 (4 ounce) packages sliced exotic mushrooms may replace the shiitake mushrooms and broccolini may replace the rapini.
If turkey tenderloin is not available, purchase a boneless turkey breast or turkey breast half, skin the turkey and cut into 1-inch chunks.
Culinary Taste Tip
Fresh rapini can be found from fall to spring in markets with specialty produce sections. It should be wrapped in a plastic bag and refrigerated for no more than five days.
Culinary Technique Tip
Italians are particularly fond of rapini, and cook it in a variety of ways including frying, steaming and braising. It can also be used in soups or salads.