1. In a large skillet, toast buckwheat over medium-high heat, shaking, until lightly browned and fragrant (3 minutes).
2. Cook buckwheat in boiling lightly salted water until just tender (5-7 minutes); drain.
3. In a large bowl mix vinegar, oil, 1/2 tsp salt, and ground pepper. Add warm buckwheat, bell pepper, mango, onion, and parsley; toss. Serve on greens.