Start by preheating a griddle pan in Roccbox and rub the sliced bread generously with olive oil. Pop the oiled bread in the hot pan and toast in Roccbox for 2-3 minutes, flipped over halfway through. Set to one side.
Pop the veal bones into a cast iron pan with the marrow facing upwards and cover with foil. Put the tray into Roccbox for 4 minutes.
Rotate the pan 180 degrees and cook for a further 4 minutes.
Check the marrow is cooked and score with a small knife into a diamond pattern. Sprinkle each piece of marrow with a generous pinch of sea salt and top with the chives and shallots.
Spoon the marrow out and spread on toast to eat.