Cardamom-Scented Lamb with Mashed Sweet Potatoes

Preparation

1. For sauce:

   Step 1

   Melt 1 tablespoon butter in heavy medium saucepan over medium-high heat. Add tomato paste, garlic and thyme; sauté 1 minute. Add wine and boil until reduced by half, about 8 minutes. Add both broths; boil until reduced to 1 1/4 cups, about 10 minutes. (Can be made 1 day ahead. Cover and refrigerate.)

2. For lamb:

   Step 2

   Preheat oven to 450 °F. Toast cardamom seeds in heavy small skillet over medium heat until fragrant, about 2 minutes. Cool. Transfer to spice grinder; grind coarsely.

   Step 3

   Sprinkle lamb with cardamom, salt and pepper. Heat oil in heavy large skillet over high heat. Add 1 lamb rack; sear until brown, turning occasionally, about 6 minutes. Transfer lamb, meat side up, to baking sheet. Repeat with second lamb rack. Roast until meat thermometer inserted into center registers 125°F for medium-rare, about 18 minutes. Let stand 5 minutes. Cut lamb between bones into chops.

   Step 4

   Bring sauce to simmer. Reduce heat to low. Add butter and mustard; whisk just until butter melts. Season with pepper. Spoon sauce onto plates. Top with sweet potatoes and lamb and serve.