Preheat your oven to 350*F. Take your leftover mashed potatoes out of the fridge to come to room temperature.
Heat a pan over medium and add the butter and oil. Once hot, add your leeks and vegetables and cook for 3-4 minutes, stirring.
Add the meat and cook for a minute more. Put your flour in the pan and stir to coat the meat and vegetables.
Pour your broth into the pan, bring to a simmer, and cook for 8-10 minutes, until it is thickened. Stir occasionally to keep it from scorching.
Remove from the heat and allow to cool for 5 minutes before stirring in the coconut milk. Transfer the filling to a 9x13 pan.
Stir the cheese into mashed potatoes, then dollop across the top of the filling. Put in the oven and bake for 20-25 minutes, until fully hot.