1 dried ancho chile, stemmed, seeded, coarsely torn2 Tbsp vegetable oil1 cup chopped onion1 Tbsp tomato paste3 garlic cloves, minced½ cup dry red wine½ cup ketchup1 Tbsp apple cider vinegar1 Tbsp dark brown sugar2 tsp Worcestershire sauce¼ tsp ground cuminPlace chile in medium bowl and cover with boiling water, soak until soft, about 30 minutes. Drain (save water). Heat oil in heavy saucepan. Add the onions and sauté until soft, stirring often. Add tomato paste; stir 2 minutes. Add garlic and stir 30 seconds. Add wine and softened chile, then simmer 2 minutes. Add 3 tablespoons saved chile soaking water, ketchup, and all remaining ingredients. Simmer 3 minutes, stirring often. Season with salt and pepper. Remove from heat and cool slightly. Puree sauce in blender, adding more reserved soaking liquid by tablespoonfuls if too thick. Cover and chill.Toss your prawns with 3 parts sauce and 1 part mayo. Grill and serve immediately.
