First begin by preparing your loaf pan. Use a standard sized pan and concentrate your mixture in one corner, or use a mini loaf pan. Line with parchment paper.
Dice your butter finely and let sit at room temp until soft and workable, then smooth with a spatula in a mixing bowl.
Prepare radish by washing and patting dry. Slice off both ends to create cylindrical shapes.
Spread a layer of butter at the bottom of your loaf pan enough to hold the radish. Press it gently into the butter layer so they stand upright. Fill in all of the gaps with remaining butter using a small offset spatula or other utensil and do your best to pack it tightly so no air bubbles remain.
Once packed, refrigerate for 3 hours minimum, or overnight.
When ready to slice, remove from the loaf pan using the parchment paper and then square off any rough edges. Slice into thick squares or rectangles and serve with bread and a sprinkle of salt.