Combine ingredients to make sauce.
Slice beef into thin strips. Cover with ⅓ of marinade and reserve the rest. Marinate 2 hours.
Slice bell pepper and onion.Cook in large skillet over MH heat with about 2 T olive oil. Stir frequently for about 8 minutes, then reduce heat to ML and let cook for 5 more minutes.
Move peppers and onions to the edges of the skillet and add the meat to the middle. Let cook 2 minutes, then stir and cook another 2 minutes.
Add reserved sauce and stir everything together. Add the mangoes to the skillet and let cook for 8-10 minutes on low heat.
Top as desired.