Method

1. Peel onions and submerge in buttermilk. Leave for 48 hours at room temperature. This starts the culture fermentation. This is also known as lacto fermentation. Then refrigerate for a further 48 hours. This develops flavour and the acids break down the cells of the onion. The texture of the onion should still be crisp but the flavour has settled and somewhat pickled it.
2. Bring water to the boil, add bonito and let sit for 10 min, strain. Sweat ginger and eschallots until fragrant and soft. Add sake, mirin and water. Simmer for 15 min. season with the soy sauce. It make need a little more, it may need a little less. Cool.
3. Slice eschallots thinly. Cover with oil and bring to a simmer. Simmer for 10 minutes until the shallots start to change colour. Remove and allow to cool. Strain.
4. To serve fill fermented onions with soy mirin bonito dressing. Top with shallot oil and toasted sesame seeds