Melt the butter and whisk it through the soy sauce. Taste and add a little more soy sauce, if you like. Pop it in the fridge to set while you make the soup.
Put the canned beans (with their liquid) into a blender with the remaining ingredients. Blend until smooth and the fats have emulsified, which will make it extra creamy.
Pour the blended mixture into a pan. Fill the empty bean can halfway full with water, then tip this into the pan. Add more water if you like, depending on how thick you like your soup. Heat through well and season to taste. Add an extra bit of vegan butter to give it a velvety texture, if you like. You can also add a bit more miso paste if you think it needs it.
To serve, top the soup with chilli oil and sesame seeds. Toast the bread and spread it with the soy butter, if using.
