Slow Roast Lamb with twice cooked potatoes and tray gravy

Slow Roast Lamb with twice cooked potatoes and tray gravy

This deceptively simple recipe for slow roast lamb is a guaranteed crowd pleaser, perfect for a decadent Sunday feast. Admittedly, the orchestration of cooking the lamb, crispy roast potatoes & tray gravy does require a bit of a dance near the oven. However, the true beauty of this recipe is that the majority of the preparations are done well before your guests arrive. Leaving you to toss a simple rocket salad & relax with your dinner party crew. As with most of my recipes, the ingredients are to be used as a guide not a rule. Cooking should be an expression of your creativity & for using what you have. Short on onions ? Use a base of carrots, celery & garlic instead. Don’t like rosemary ? Substitute with fresh thyme & oregano. Forgot the lemon? Use a quarter of an orange for the subtle burst of citrus in the gravy.

For the Lamb & tray gravy:

  • 2.5kg leg of lamb on the bone
  • 2 large onions thickly sliced (or 3~4 smaller onions, halved)
  • 4 large cloves of garlic
  • 1/2 a lemon
  • 3 fresh sprigs of rosemary
  • 3 cups bone broth
  • 2 cups boiling water
  • Olive oil, salt & pepper to season

For the Potatoes:

  • 1kg farmer fosters potatoes, soaked & scrubbed, then halved or quartered depending on size
  • Ghee or olive oil to coat


Take the leg of lamb out of the fridge & bring up to room temperature (approximately half an hour before you begin to cook) Preheat oven to 160c (fan forced) Place the thickly sliced onions, garlic, lemon & 2 sprigs of rosemary on the base of a deep roasting dish. This will form the flavour base for the gravy, as well as the platform for the lamb to cook on. Pat the lamb dry with paper towel & place thick side down on the onions (the side closest to the bone should be at the top, as this ensures the thickest part of the meat roasts slowly in the onion & garlic infused broth, resulting in tender, decadently flavoured meat. Drizzle the lamb with olive oil & sprinkle with salt & pepper. Pour the bone broth & boiling water around the lamb, the onion base should be almost completely submerged. Cover the tray with foil, sealing tightly around the edges. Pop in the oven for 4.5 hours.

Remove lamb from the oven & increase temperature to 200c (fan forced) The lamb at this point should be fork tender, with a lot of liquid in the roasting pan. Carefully turn the lamb over so the thickest part of the meat is now facing upwards. Drizzle with olive oil, salt & pepper & a sprinkle the leaves of the remaining rosemary sprig. Return the lamb to the oven for between 30 ~ 45 minutes, or until the top has roasted a deep golden brown.

At this stage, place a baking sheet on the bottom shelf of the oven to preheat for the potatoes. Whilst the lamb is finishing roasting, add the prepared potatoes to a pot & cover with water. Bring to the boil & cook for approximately 15 minutes. A fork should be able to be inserted without too much resistance. Drain the potatoes & allow to steam dry in the colander. This ensures that they form a crispy crust !

Remove the lamb from the roasting tray, & place in a dish. Cover tightly with foil & then tuck under a clean tea towel (or two!) to keep warm whilst you finish the potatoes & gravy. Slide the roasting tray with the onions, aromatics & broth onto the bottom shelf of the oven to reduce the liquid & create a rich jus. If a really thick gravy that clings to the meat is your vibe, you can add a teaspoon of tapioca starch mixed with a little dash of water to the pan, giving a brisk whisk to ensure there’s no lumps before returning to the oven.

Coat the dried potatoes in generous lashings of ghee or olive oil & place on the preheated baking sheet. Listen to that satisfying sizzle & REFRAIN from salting the potatoes. Seriously, step away from the salt. Salt somehow stops the potatoes forming a truly crispy crust! Pop the potatoes on the top shelf of the oven & roast until deeply golden & crispy.

Season liberally. Plate up lamb, potatoes & gravy to serve family style on your feasting table 🤍

Image and recipe by Jessica Bull