Preheat the oven to 180°C. Slice beef into 2.5-3cm cubes. Season with salt and pepper, add about 2 tablespoons of oil and mix well. Heat a large frypan over a medium-high heat. Brown the beef in 2 or 3 batches. Remove each batch and place in a casserole dish.
Reduce heat in pan to medium and add a little extra oil. Add the garlic, ginger and curry paste, cook for 1-2 minutes, stir often. Pour in the stock, stirring well. Pour the mixture over the beef in the casserole dish and stir to combine. Cover the casserole dish and place in the oven. Stir every 40 minutes or so, adding a little water if needed to keep the ingredients just covered. Cook until the beef is almost tender (about 90 minutes).
Add the diced tomatoes and yoghurt, mix well. Cook for a further 30 minutes, or until the beef is very tender. Serve sprinkled with a handful of mint leaves.