Preheat the oven to 200ºC/400ºF/gas 6. Line two trays with greaseproof paper and rub with olive oil.
Melt the chocolate in a heatproof bowl over a pan of gently simmering water, then remove and stir in the butter so it melts.
Tear the bread into a food processor and blitz into fine crumbs, then add the eggs and sugar, and blitz again well. With the processor still running, pour in the chocolate mixture and let it blitz until combined.
Spoon the cookie mix into a large sandwich bag, snip off the corner and pipe 3-4cm blobs to make 24 cookies on the lined trays.
Bake for 8 to 10 minutes, or until spread and set. Sprinkle with sea salt, leave to cool a little, and tuck in.