Seal beef short rib in a well-oiled pan until golden brown on all sides.
Vacuum pack short rib with all ingredients and cook at 60°C for 72 hours. (You can speed up this process by baking short rib with other ingredients, covered with tin foil for 6 hours at 140°C)
Cut down short rib and reduce remaining liquor till thick, then glaze portions of short rib.
Peel, cut down potatoes and cook in a saucepan covered with cold water and the salt.
Bring potatoes to a simmer and cook for 20 minutes then pass through a sieve using the back of a spoon.
Cook the parsley in boiling water for 3 minutes, squeeze out excess water and blend until smooth.
Beat potatoes in a pan with a spatula on a medium heat for 3 minutes.
Add cream, wasabi paste and butter and cook for a further 2 minutes.
Finish mash with parsley puree then place on a plate.
Top with beef short rib followed by the glaze.