Tear the stale bread into pieces and put them in a blender with the vinegar, caper brine (or water) and extra-virgin olive oil.
Add the capers and anchovies, if using, and pop in the garlic.
Finely chop the parsley stalks and roughly chop the leaves, add these to the blender, too.
Pulse-blend to a coarse but evenly textured paste.
Season and store in a clean jar in the fridge, where it will keep for up to a week.
