Chop the caperberries, onion, garlic and herbs as finely as you can.
Add the room temperature butter to your mixing bowl as well as the finely chopped ingredients and the paprika, Dijon mustard and tomato ketchup. Mix and fold together until completely incorporated.
Lay a roll of cling film out over a clean, slightly damp table top (this helps it to stay firm when it's rolled up) and add the butter in a sausage-like shape across the width of the cling-film. Make sure to allow at least an inch of space on either side.
Roll up the roulade of butter, tightening the edges of the cling film until the roll becomes firm. Now return it to the refrigerator to chill and harden. Once hardened, it is ready to be removed and sliced. Make sure not to leave any cling film behind on the butter. Allow the discs to reach room temperature before placing on the cooked steak.
Cook the steak to the doneness of your choosing. Garnish the steak with disks of butter to allow them to soften and melt further on the steak while it is resting.