Heat the oven to 200C (180C fan)/390F/gas 6. Chop the courgettes into roughly 2cm pieces, put in a large roasting tray, drizzle with olive oil, add the garlic and chilli, and season well with salt and pepper.
Finely chop half the lemon and its rind, discarding any pips as you go, and add to the tray. Squeeze the juice of the other half over the courgettes and pop the squeezed half into the tray, too.
Roast for 40 minutes, tossing halfway through.
Remove the courgettes from the oven, squeeze the garlic out of its skin into the tray, and leave to cool a little.
Roughly chop the parsley on a large board, add the courgettes and chop together until you have a creamy dip – you can use a food processor if you prefer. Scoop on to a serving plate and scatter over the mint leaves. Serve at room temperature with flatbreads or crudites for dipping.