Prepare the lemon and rosemary: zest both lemons first (zest releases bright oils that give an immediate lemon perfume) and then juice them into a small bowl. Finely chop the rosemary and set aside. Doing zest before juicing is easier — it's hard to zest a squeezed lemon.

Warm and lightly crush the chickpeas: place the 400 g cooked chickpeas in a medium mixing bowl. Use a fork or a potato masher to gently crush about half the chickpeas — leave the rest mostly intact for texture. Crushing releases starches so the mixture becomes creamy and helps it bind on the bread while retaining pleasant chickpea bite.

Make the lemon-rosemary dressing: to the crushed chickpeas add the lemon zest, 2 tbsp of the lemon juice (reserve remaining juice for adjusting), the chopped rosemary, 3 tbsp of extra-virgin olive oil, a small pinch of sea salt and a few grinds of black pepper. Mix and taste. The acid from lemon brightens the chickpeas while the olive oil gives body; seasoning at this stage ensures the base is flavorful before assembly.

Adjust texture and seasoning: if the mixture seems dry, add up to 1 more tablespoon of olive oil or the remaining lemon juice to reach a soft, spoonable consistency. Season with salt and pepper — chickpeas often need more salt than you expect to bring out their flavor. The goal is a cohesive spread that’s lively (lemon) and aromatic (rosemary).

Toast the ciabatta: brush both sides of each ciabatta slice lightly with the remaining 1 tbsp olive oil. Heat a large skillet over medium-high heat or preheat the broiler. Toast the slices 2–3 minutes per side in the skillet until golden and crisp (or broil 2–3 minutes per side), rotating once. Toasting dries the surface so the topping doesn’t make the bread soggy and creates pleasant chew and char.

Rub with garlic (optional): while the toast is still warm, rub the cut side of the garlic clove across the top of each slice. The gentle rubbing deposits a whisper of garlic flavor without overpowering the delicate lemon-rosemary notes — a classic bruschetta technique.

Assemble the bruschetta: spoon a generous 3–4 tablespoon portion of the lemon-rosemary chickpea mixture onto each warm toast. The warmth helps release aromas and melds flavors. Pile about 20 g (a small handful) of baby arugula on each slice — the peppery arugula adds crunch and contrast.

Finish and serve: Finish each bruschetta with a small drizzle of olive oil, a quick grind of black pepper and a light pinch of flaky sea salt. Serve immediately so the toast stays crisp and the chickpea topping is bright and fresh.