In a large non-stick pan, heat oil over medium high heat. Add onions and cook until tender. Stir in ginger and garlic and cook until aroma is released. Stir in curry powder, coriander and cumin and continue to cook until aroma is released. Stir in carrots and potatoes and toss to coat. Stir in tomatoes and chicken stock and simmer until carrots and potatoes are tender. Add green beans and simmer for 1 minute. Stir in coconut milk and cilantro. Serve warm with rice.