Slice the kimchi into small pieces. Drain excess liquid from the kimchi by letting it sit in a sieve above a bowl for 20 minutes. Save the delicious jus for an extra funky Bloody Mary.
Grate the potato coarsely, directly onto a clean tea towel.
Wrap the towel around the grated potato and wring vigorously to for about 30 seconds to remove moisture. Mix the drained spuds and kimchi in a bowl.
Melt 50g of butter in a pan on medium high heat pan for 2 minutes. Spread the kimchi potato mixture across the pan in a pancake shape.
Cook on medium high heat for 2 minutes then turn down to medium low. Cook for about another 6 minutes on medium low.
While it is cooking, prep the hollandaise - put all the ingredients except the butter in a jug or glass tall enough that an immersion blender reaches the bottom - use the blender to give it a mix. Keep the blender on and slowly add the butter til you have a thick, silky hollandaise. Alternatively use a food processor.
Grab a plate around the same size as the frying pan, invert the whole thing, tap the bottom of the pan with the hilt of a knife to loosen the rosti and turn it onto the plate.
Put the rest of the butter in the pan on medium high heat and let it melt for a minute before sliding the rosti back onto the pan golden brown side up. Cook for two minutes on this heat. Turn down to medium low and cook for another 5 minutes.
While the rosti finishes cooking, fry one egg per person to their liking on another pan.
Cut the rosti into slices, and serve with a fried egg and a dollop of gochujang hollandaise.
