In a suitably sized saucepan, heat the butter and the oil.
Saute the onions until they soften, then add the garlic and cook for one minute.
Stir in the curry powder, cumin and flour; then cook for a few seconds.
Whisk in the chicken broth and cook, stirring continuously, until thickened.
Add the cooked lamb cubes and heat though.
Serve with white rice.