Preheat the oven to 220C / 425F / gas mark 7.
Arrange the peppers, courgette, aubergine and cherry tomatoes on a large baking tray. Drizzle with olive oil and season with salt and pepper.
Roast for 30-35 minutes, turning halfway through, until tender and caramelised.
Place the chickpeas in a bowl and lightly mash them with a fork, leaving plenty of texture. Stir in the vegan yogurt, lemon juice, capers, parsley, Dijon mustard, and season to taste.
Slice the focaccia horizontally and lightly toast the cut sides under the grill or in a dry frying pan for 2-3 minutes.
Spread the crushed chickpea mixture generously over the bottom half of the focaccia.
Top with the roasted vegetables.
Drizzle with balsamic glaze and scatter over fresh basil leaves, if using.
Place the top half of the focaccia on top, press gently, then slice and serve.