Combine the mince, egg, spice mix, salt, chopped coriander and half the tin of rinsed beans. Using your hand, mix the meatball ingredients together until well combined. It’s ok if you squash some of the beans as this helps bind the meatballs.
Divide the mixture into 8 equal portions, or use a ⅓ cup measure, and roll each meatball into a football shape. Place onto a plate and refrigerate for 15 minutes.
Put the 2 tablespoons of oil into a skillet that’s big enough to take the meatballs with room between each. Swirl the oil around to coat the skillet, then place each meatball into the oiled skillet, turning each over to coat with the oil. Put it all into the oven as you make the sauce.
Heat the oil over medium flame. Sauté the onions until soft and translucent, or about 5 minutes, stirring occasionally.
Add the puréed tomatoes, water, remaining kidney beans, spice mix and chilli. Stir to combine and bring to a simmer. Check the seasoning and allow to cool gently for 10 minutes, stirring occasionally.
Remove the skillet holding the meatballs from the oven. Scoop the sauce over each meatball then pour the remaining sauce around them. Put the skillet back into the oven and cook for 25 minutes.
Serve immediately garnished with coriander leaves.