Melt butter in a pan. Add in onions and saute until soft and fragrant. Add in meat, vegetable, and spices. Cook for another minute. Have a taste and season with salt. Add water and sprinkle in the flour. Cook until the filling is slightly thickened. Remove from the heat and let it cool down completely. Can be prepared one day ahead.
Boil the potato until soft (you can easily pierce with fork). Mash it while it's hot using potato masher or using mixer. Add the milk powder and the rest of the ingredients. Stir to mix everything. Set aside to let it cool down
Preheat cooking oil enough for deep-frying. Clean your hands thoroughly and it's easier if your hands are a bit wet. Take about 1-2 Tbsp of potato dough and flattened it on your hand and make a little well in the middle. Fill with the filling (don't over fill or you will have trouble wrapping it up) and close it by molding the dough around the filling to form a croquette shape
Dip in eggs and then bread crumbs. Fry in small batches 2-3 at a time for best result
Kroket Kentang / Indonesian Potato Croquette https://whattocooktoday.com/kroket-kentang-potato-croquettes.html