Heat butter and olive oil in a large pot over high heat.
Fry onion and garlic until fragrant.
Add curry powder, garam masala, salt, and tomatoes; fry for a minute.
Add chicken stock and brown rice, simmer covered for 1.5 hours, stirring occasionally.
Add apple, carrot, and sweet potato; simmer for another 30 minutes.
Adjust seasoning with salt if necessary.
Stir in shredded chicken and yoghurt.
Serve topped with chopped coriander.