1/4 teaspoon cornstarch, dissolved in a little water
Minced basil leaves or flat-leaf parsley, for garnish
Blend yogurt, Worcestershire sauce, lemon juice, cardamom, salt and pepper together in a non-reactive bowl. Reserve 1/2 of the mixture for later use. Add lamb cubes and stir to cover evenly. Cover and marinate in refrigerator for 2 hours or up to 2 days, turning occasionally.
Turn on broiler and position rack about 4-5 inches from heat.
Lift meat from yogurt mixture. Thread 3 cubes of meat, 3 half onions and 3 pieces of pepper on each skewer in an alternating pattern. Place on broiler pan and broil for about 6-9 minutes, depending on size.
Meanwhile, put reserved marinade into a small saucepan. Add Red Pepper Jelly and heat over medium-high heat to melt jam. Whisk in cornstarch and stir until smooth. Season with salt and pepper.
Serve 1 or 2 kabobs to each person. Drizzle on minced basil; spoon on sauce and serve.