To make the roux, heat the butter in a small saucepan over medium-high heat. When the butter is starting to foam, add the flour. Cook, stirring, for 2-3 minutes or until the mixture has darkened slightly. Stir through the curry powder and garam masala. Cook for a further 2 minutes. Then transfer the mixture to a bowl and set aside for later. To make the curry sauce, heat the oil in a large wok or saucepan over medium heat. Add the garlic and onion. Season with a pinch of salt and cook, stirring every so often, for 2-3 minutes. Then stir in the roux. Now add the chicken and mix until well coated. Then add the soy sauce, honey, vinegar, apple juice and chicken stock. Add the potatoes and carrot. Bring the curry to a simmer. Then turn the heat to low and simmer with the lid off for 45 minutes or until the vegetables are tender and the curry sauce has thickened. Taste and season with salt and chilli powder to taste. Remove from heat and serve with steamed rice and pickled ginger if using. *NOTES: Garam masala is an Indian spice blend you can find the in spice section of most supermarkets or order online.