For The Topping For The Filling

1. Preheat oven to 190C.
2. Bring a medium pot of water to a boil. Add the peeled and chopped sweet potatoes and boil until they are very tender (10-12 minutes). Drain and return to the pot. Mash then add butter, milk and 1/2 tsp salt. Stir to combine.
3. Meanwhile, heat a large oven-proof skillet over medium heat. Add beef, onion, mushrooms, carrot, bell pepper, garlic and 1/2 tsp salt. Cook while stirring frequently until the beef is browned and the carrots are tender (15 minutes).
4. Stir in tomato paste, chili powder, paprika, dried thyme and remaining 1/4 tsp salt. Cook for roughly a minute. Stir in balsamic vinegar, water & peas.
5. Spread the sweet potato mixture over top of the filling, bake for 10 minutes and broil for 2-3 minutes until the top has slightly browned.