Mix the parsnip, carrot ( or beetroot), onion and cabbage together in a large mixing bowl and add the big pinch of salt. Squeeze as much liquid out of the vegetables as you can, then divide into two equal portions.
Add the potatoes, eggs and flour to one portion, seasoning with salt and pepper. Mix well and press this into eight thin equal sized patties ( rostis ).
Heat a couple of tablespoons oil in a non stick frying pan over a moderate heat. Working in batches, fry the patties for about 3 minutes on each side until crisp and golden all over. Put the fried patties on to a plate lined with paper towels and keep warm while you cook the remaining batches.
Meanwhile mix the remaining vegetables with the creme fraiche and mustard. Set aside.
To serve put two rostis on each plate, pile on some slaw then add sausages and some good mustard on the side.