Start this recipe a day ahead to chill the rice bran oil for the green mustard and to freeze the smoked garlic.
Note Smoked garlic is available from Harris Farm Markets. If the octopus hasn't been tumbled, place in the freezer overnight to tenderise it. If clean seawater is unavailable dissolve 2 tsp fine sea salt in 1 cup water). Mustard greens, usually known as gai choy, are available from Asian grocers.