Ingredients

• 3 red-skinned sweet potatoes (yams; about 2 1/2 pounds)
• 1 teaspoon (or more) hot prepared Chinese mustard
• 1 cup balsamic vinegar
• 1 1/2 teaspoons soy sauce
• 1 pound Chinese broccoli or broccoli rabe (rapini),* large outer leaves removed, cut crosswise on diagonal into 1/4-inch-thick slices
• 2 slices bacon, cut into 1-inch pieces
• 2 teaspoons yellow mustard seeds
• 4 5- to 6-ounce arctic char fillets
• 2 tablespoons vegetable oil, divided

Instructions

1. Preheat oven to 400°F. Wrap sweet potatoes individually in foil. Roast until tender, 1 to 1 1/2 hours. Cool and peel. Puree in processor until smooth. Measure 3 cups puree and transfer to microwave-safe bowl. Stir in mustard. Season with salt. DO AHEAD: Can be made 1 day ahead. Cover and chill. Boil vinegar in small saucepan until reduced to ` cup, about 8 minutes. Stir in soy sauce. Remove from heat.
2. Cook broccoli in pot of boiling salted water until crisp-tender, about 1 minute. Drain; set aside. Cook bacon in medium skillet over medium heat until edges are crisp. Transfer to paper towels to drain. DO AHEAD: Reduction and broccoli can be made 2 hours ahead. Let stand at room temperature.
3. Process mustard seeds in spice grinder until coarsely ground. Sprinkle fish with salt and pepper. Sprinkle ground seeds over top of fish. Heat 1 tablespoon oil in large skillet over medium-high heat. Add fish, mustard side down, and cook until brown and just opaque in center, about 3 minutes per side.
4. Meanwhile, rewarm puree in microwave until heated through. Heat 1 tablespoon oil in another large skillet. Add broccoli and bacon; sauté until heated through. Season with salt and pepper.
5. Divide broccoli, fish, and puree among plates. Drizzle with balsamic reduction and serve.
6. *Chinese broccoli is also called gai lan or Chinese kale; it's available at Asian markets. Broccoli rabe is an Italian leafy green vegetable with scattered clusters of broccoli-like florets; you'll find it at some supermarkets and at specialty foods stores.