Dice the onion, finely chopping for best texture. Coarsely chop the olives. Mince the capers.
Combine the chickpeas with the olive oil, tahini, mustard, 2 tsp/10ml vinegar, and 1 tsp/5ml maple syrup. Use a potato masher to smash the chickpeas into coarse bits. Alternatively, place ingredients in a food processor and pulse until chickpeas start breaking up. Do not puree fully. If still too dry, add 1-2 tbsp/15-30ml water (or pickle juice or liquid from canned roasted red peppers for extra flavour).
Mix in the salt, dill, and black pepper. Taste and adjust vinegar and maple syrup as needed (olives and capers will make the mix saltier so don’t adjust salt level yet).
Fold in the chopped onions, olives, and capers.
For optimum flavor, toast the bread. The crunch of toasted bread matches really well with the softer chickpea mixture and vegetables.
Place a 1/2 – 3/4”/12-18mm thick layer of smashed chickpea filling on one piece of bread. Layer on lettuce and a single layer of roasted red peppers.
Make ahead: The smashed chickpea filling can be made in advanced and store in the fridge for up to 3 days. For best results, assemble sandwich just before eating.
Notes
Pickles instead of olives: Swap the olives for dill pickles and reduce the dill to 1 tsp/1g.Maple syrup: A small amount of sweetness helps balance out the salty and savory preserved elements. The filling shouldn't be sweet, just a hint of maple syrup.