Preheat the oven to 190 degrees Celsius.
Dry roast the buckwheat in a frying pan. Bring 3 cups of water to the boil and add the buckwheat, lentils and a pinch of sea salt. Cover, reduce the heat and simmer for 15 minutes.
Heat 2 tbsp sesame oil in a large frying pan and sauté the mushrooms for 5 minutes until soft. Remove from the pan and set aside. Add the remaining sesame oil and sauté the garlic, ginger, onions for a further 5 minutes.
Bring a large pan of salted water to the boil and add the cabbage leaves to blanch for 1-2 minutes. Rinse under cold water and blot dry. Line the bottom of a loaf tin with the cabbage leaves leaving enough over the sides to fold over the top and cover the loaf.
In a large bowl, combine the buckwheat with the vegetables and roasted nuts. Mix together the arrowroot, flour, and miso paste with a little water until smooth and stir into the buckwheat mixture. Finally combine through the herbs, and chopped bread.
Fill the loaf tin with the mixture and press down firmly. Cover the loaf with the cabbage leaves. Cover with foil and place the loaf tin into a baking dish filled with enough water to come halfway up the loaf tin. Bake for 45 mins or until firm to the touch.
Cool slightly, remove foil and turn onto a serving plate.
Note: arrowroot is a natural thickener derived from the root of a South American plant. It has twice the thickening power of regular wheat flour and is gluten free.