Prepare smoker for cold smoke.
Place breasts on a smoker rack and put in smoker for 15 minutes. Remove from smoker.
In a small bowl, add fresh lime juice to sour cream and stir. Season with salt, to taste. Refrigerate until ready to serve.
Preheat oven to 350 degrees F.
Place duck breasts in saute pan and place in oven. Roast duck for 10 minutes or until medium-rare. Remove from oven and cool.
Using a sharp knife, dice duck breasts into 1/2-inch pieces.
Place oil in a large saute pan over medium high heat. When hot, add onions and saute for 3 minutes or until onions are translucent. Add diced duck, season with salt and pepper. Stir in barbecue sauce, bring to a boil, and immediately remove from heat.
Place four flour tortillas on a clean work surface. Divide the duck mixture onto the tortillas to cover. Sprinkle mango, poblano, red onion, cheese, and cilantro evenly over duck mixture. Top with the remaining flour tortillas and brush each side with a small amount of canola oil.
Bring a large saucepan or griddle to medium heat. Place one flour tortilla sandwich into pan or griddle and cook until golden brown or about three minutes. With a spatula, pick up flour tortilla sandwich and turn over to finish cooking to a golden brown. Remove from pan or griddle and place on cutting board. Cut into six wedges. Place on a warm plate and dab Lime Sour Cream on each wedge and garnish with a cilantro sprig.
Recipe courtesy of Dean Fearing, The Mansion on Turtle Creek