Mustard greens have a peppery flavor that complements the sweet and spicy sauce here, but you could use any steamed greens as the base for this tofu entrée that can be made in 30 minutes or less.
Heat oil in saucepan over medium heat. Add onion and bell pepper, cover, and cook 10-15 minutes, stirring occasionally. Stir in mango chutney and tomato. Cover, and simmer 5 minutes more.
Preheat oven to broil. Coat baking sheet with cooking spray. Halve each tofu block horizontally to make pieces the size of sandwich bread. Cut each tofu piece into 4 triangles. Brush each triangle on both sides with mango mixture and place on prepared baking sheet. Broil 4-5 minutes. Flip and brush with more mango mixture. Broil 4-5 minutes more, or until browned.
Bring 1 cup water to a boil in large pot. Add mustard greens, cover, and steam 5-7 minutes, turning occasionally with tongs.
Divide mustard greens among plates. Top each serving with 2 tofu triangles, and drizzle with 1/4 cup mango sauce.