Preheat oven to 220°C. Grease a baking tray and then line with baking paper.
Combine preserved lemon, coriander, garlic, pepper, chilli flakes, capers and 1/4 cup oil in a bowl. Add bread and parmesan, tossing to combine. Transfer to tray and bake for 20 minutes, stirring halfway, or until golden and crisp. Stir through fresh chilli.
Meanwhile, to make the dressing combine 1/4 cup olive oil, parsley, red wine vinegar and preserved lemon rind.
Preheat a chargrill or barbecue over high heat. Place asparagus and spring onion on a tray and drizzle with remaining oil. Grill for 3-4 minutes, cooking asparagus only on one side, or until grill marks appear. Transfer to a serving plate, drizzle with dressing and spoon over crumb mixture. Garnish with mint leaves and serve.