Preheat An Oven To 325F/165C. In A Large Frying Pan Over Medium-High Heat, Warm 1 Tbsp Butter Or Oil Per Serving. Working In Batches, Add The Meat And Fry, Turning, Until Browned On All Sides - About 10 Minutes. Using A Slotted Spoon Transfer To A Baking Dish Or Stew Pot. Add The Onions To The Fat Remaining In The Frying Pan And Saute Over Medium Heat Until Tender And Translucent - 8-10 Minutes. Add The Garlic, Cumin, Coriander, Tomatoes, Tomato Paste, Stock And Mint. Stir Well. Pour Over The Meat And Season To Taste With Salt And Pepper. Cover And Bake Until All The Liquid Is Absorbed - About 1.5 Hours. Taste And Adjust The Seasoning.