Pull the bread into bite-sized pieces and put it into the bottom of a large bowl. Sprinkle on 1 tbsp cold water, 1 tbsp red wine vinegar and 2 tbsp olive oil and leave it to sit for 30 minutes.Add the broad beans, celery and cucumber. Mix the anchovies with the remaining vinegar, 2 tbsp olive oil, and add plenty of pepper.
Pour this over the salad, add the capers and toss everything together. Leave to sit for 15 minutes (or more if you like), then finely chop the mint and toss through the salad at the last minute (if you do this earlier, it may turn black). Serve the salad on 4 plates with a whole burrata each (or half a large one) and drizzle over more olive oil.