Combine the mayonnaise, gherkins, capers, dill and horseradish cream in a large bowl. Add the cabbage and apple. Season and stir to combine. Refrigerate while preparing the rosti.

Steam or microwave potatoes for 3-4 mins until partially cooked. Set aside until cool enough to handle. Coarsely grate. Place in a bowl with beetroot and butter. Season. Mix to combine.

Heat a non-stick pan over medium heat. Cook 1/2 cupfuls of beetroot mixture, in batches, for 5-7 mins each side or until crisp and golden.

Stack 2 rosti on each plate. Top with prosciutto slices and extra dill sprigs. Serve with slaw and lemon wedges.

NOTE: Make sure you only partially cook potatoes before grating, or the rosti mixture will be too soft to hold together during cooking.