Preheat the oven to 200°C.
Squeeze excess water from grated potatoes using a clean tea towel.
Combine the potatoes, beetroot, crème fraîche, egg yolk, parsley, salt, and pepper in a bowl.
Heat 75g butter in an ovenproof pan and place two 7.5cm rings inside.
Spoon the mixture into rings and fry for 4 minutes per side until golden.
Bake the rosti in the oven for 10 minutes until tender.
Blend egg yolk, lemon juice, and water, then slowly pour in warm clarified butter to thicken.
Season the hollandaise with cayenne pepper and salt.
Fry the corned beef in 50g butter for 3 minutes per side until crisp.
Fry the duck eggs in rapeseed oil until cooked to your preference.
Stack the corned beef and egg on the rosti and drizzle with hollandaise.