Preheat oven 300 degrees.
Sear pork belly fat side down on medium heat, place into a roasting pan 5 L capacity.
Add mustard, juice, orange, onion, celery, carrot and cover with chicken stock, foil wrap pan and cook for 3 hours till tender. Cool in liquid. Strain braise liquid and add miso paste, set aside. This can be made up to 3 days prior to serving.
Preheat oven to 400 degrees. Cut pork belly into equal portions and put skin side down into a sauté pan and put in oven for 30 minutes till hot; then add ½ cup braise and add butter slowly to create glaze, baste pork till syrup consistency and serve with a green salad.