Roughly chop the garlic and rosemary, combine with the lemon rind and 1 teaspoon of salt and rub over the lamb. Stand at room temperature for 1 hour (longer in the fridge).

Heat your oven to 200°C (180°C fan-forced). Place the potatoes in a large saucepan and cover with cold water. Bring to a boil, turn down the heat and simmer for about 10 minutes, until a sharp knife can be inserted into the potatoes and withdrawn easily. Drain the water and allow the potatoes to sit in the hot pot for a few minutes while the steam escapes. Place the lid on the pot and shake to rough up the edges of the potatoes. 

Rub the pumpkin with olive oil and toss the potatoes in the remaining oil. Season both well with salt and place in a large roasting tray. Place a wire rack on top of the roasting tray and place the lamb on top of that. Roast for 1 hour, allowing the drippings from the lamb to fall onto vegetables below. Remove the lamb from the oven, stir the potatoes, place the butter on top of the pumpkin, then return the tray to the oven to cook the vegies for a further 15 minutes while the lamb rests. Don't skip resting the lamb, otherwise the meat will be dry and tough.

For the coriander, mint and lemon sauce, combine the sugar with 1 tablespoon of hot water, stir, then add the remaining ingredients, stirring to dissolve the sugar and salt.

Cook the peas according to their packet directions. Slice the rested lamb. Remove the vegetables from the oven, cut the pumpkin into pieces, season it and the potato once more with salt, and serve with the peas and sauce. 

Also try: Adam Liaw's Tim Tam mousse

Find more of Adam Liaw's recipes in the Good Food Favourite Recipes cookbook.