Preheat oven to 175 C / Gas 3/4 and grease a casserole dish.
Bring a saucepan of salted water to the boil then add the potatoes and boil for 10 minutes, until soft. Drain, mash and mix in soured cream, salt, pepper and nutmeg. Set aside.
Meanwhile heat the oil in a frying pan, and the onion and cook and stir until translucent. Add the minced beef and fry, breaking the meat into little pieces with a spoon. When the meat is browned on all sides, add the garlic and fry for a further 1 minute. Season with salt and pepper to taste and remove from the heat. Allow to cool.
As soon as the meat is cooled, stir in the edamame and eggs and transfer the mixture to the prepared casserole dish. Top with a layer of mashed potatoes and sprinkle cheese on top.
Bake for 20 to 25 minutes in the preheated oven, until cheese has melted and the top is golden brown. Remove from the oven and serve piping hot.