For the Malay-style lamb stew, heat the oil and butter in a large enough pot and sauté the onions until translucent. Then brown the lamb meat lightly as well.
Then add the tomatoes, salt and chili powder and simmer gently with the lid on for about 1/2 hour over medium-low heat. Stir frequently.
Mix curry, sugar and vinegar with 1/8 l water and add as well. Stir well. Add the peeled and diced apple to the pot and continue to simmer with the lid closed (1-2 hours) until the meat is well done.
About 10 minutes before the end of the cooking time, add the well rinsed, strained beans. If the mixture becomes too thick, add water.
Arrange the For the Lamb Pot Malay Style and serve.