Peel and finely chop the garlic. Trim and roughly chop the celery and broccoli. Pick the mint leaves, then finely chop most of them, saving a few baby leaves to garnish. Heat a splash of oil in a pan, then soften the garlic and celery for about 2 to 3 minutes, then add the broccoli and stock. Continue cooking for another 5 minutes, then blitz with a handful of mint in a food processor. Season and serve, then crumble over the ricotta and scatter with the reserved mint leaves.