Fry the leeks in the oil in a covered pan on the lowest heat for about 15 minutes or until really soft but not browned.
Add the garlic and carrot and fry for a further minute.
Add the stock and tomatoes and simmer, covered for about 10 minutes until the carrots are softening.
Add the aduki beans, thyme and kale and simmer for a further 5 minutes until the kale is just cooked. Check for seasoning and add salt and pepper to taste. Leave to cool a little and absorb flavours while you cook the potatoes.
Bring a large pan of water to a boil, add a pinch of salt and the potatoes. Simmer for about 10 - 20 minutes until the potatoes are fork soft. Drain well. Return to the dry pan add butter and mustard and mash until soft and fluffy.
Put the filling into an oven proof dish (I used a stoneware loaf pan), top with the mashed potato. Fluff the potato with a fork and bake in the preheated oven for 25-35 minutes until browned and crisp on top.
Nutritional information is only an approximate guideline. Calculations will vary according to the ingredients you use and your cooking methods.