Shred the beef, then roughly chop the parsley leaves, chives and gherkins.
Place in a large bowl with the mashed potato, mustard and a pinch of sea salt and black pepper, then mix until combined.
Using your hands, roll it into four balls, before flattening each one into a patty.
Set out three shallow dishes. Put the flour in the first and season, beat the eggs in the second, and add the panko breadcrumbs in the third.
Roll each patty in the flour, then the egg, shaking off any excess, then the breadcrumbs, until well coated. Pop them on a plate, cover with clingfilm and chill in the fridge for 30 minutes.
Heat the oil in a large frying pan over a medium heat and cook the patties gently for 4 minutes on each side, or until golden and crisp.
In a serving bowl, mix the yoghurt and Tabasco, then serve it alongside the beef hash cakes. Delicious with dressed rocket and a poached egg.