Preheat the oven to 80˚C. Use a sharp knife to peel the zest from the lemons (reserving the peeled lemons), then place on a baking tray with the peppercorns, fennel seeds, coriander seeds and salt. Bake in the oven for 2 hours until the lemon is dry. Transfer the mixture to a spice grinder and blitz to a coarse powder.Use a small, sharp paring knife to split the prawns down the back (not cutting all the way through), then gently remove the prawn intestine. Place the prawns into a medium bowl, then drizzle with a little olive oil and sprinkle with some of the lemon pepper seasoning. Mix to combine, then heat a chargrill pan or barbecue over medium heat. Grill the prawns for 2-3 minutes each side, or until just cooked through, then transfer to a serving plate.Place the remaining lemon pepper seasoning in a small bowl, then squeeze over the juice of ½ a reserved lemon, mixing to combine to a dipping sauce. Thinly slice the avocado. To eat, remove the meat from the prawns and dip in the dipping sauce. Tuck into a lettuce leaf with an avocado slice and serve.Photography by Jiwon Kim.Want more from The Cook Up? Stream all the seasons here and for free at