Tatsoi Wilted in Mustard Dressing

Cut off tatsoi bases to separate leaves. Rinse thoroughly and spin dry. Mince white part of green onions and thinly slice dark green part.
In a small bowl, whisk together lemon juice, mustard and salt. Stir in minced whites of green onions and olive oil. Taste for seasoning.
In a small skillet, warm lemon juice mixture over low heat. Add tatsoi leaves and toss to coat. Heat until leaves just begin to wilt, about 2 minutes. Remove from heat, add sliced green onion leaves and toss. Serve warm.