Preheat oven to 400 degrees.

To make filling, heat oil in a large skillet over medium heat.  Chop onion and pepper.  Add onion and pepper to skillet and cook until slightly softened, about 6-7 minutes.  Add the turkey and cook, breaking it up with a spoon until it is no longer pink.

Chop garlic, and add to skillet with chili powder, cumin, Worcestershire sauce, and tomato paste.  Stir to combine.

Stir in the flour and cook for another 1-2 minutes. Add the chicken broth and frozen vegetables. Simmer another few minutes until thickened.  Season with salt and pepper to taste.  Pour the mixture into a 9 inch pie pan or 6 individual gratin dishes.

To make topping, cook sweet potatoes.  You can do this by piercing with a fork and placing them in the microwave for 8-10 minutes until soft, turning them over halfway through.  Once cooled slightly, cut the potatoes in half and remove the skin.  Place the flesh in a bowl, along with the sour cream, chicken broth, and butter.  Mash the mixture together with a potato masher until smooth.  Alternatively, you can pass the sweet potatoes through a food mill or potato ricer and then stir in the other ingredients.  Season with salt and pepper to taste.

Spread the sweet potato topping evenly over the filling, spreading all the way to the edges.  Alternatively, you can pipe the topping on with a pastry bag.

Place the pie on a baking sheet and bake in the oven for 25-30 minutes until filling is warm and topping is lightly browned. Cool for 15 minutes before serving. Garnish with cilantro.