Preheat oven to 180°C/350°F (160°C fan).
Season lamb – Spread lamb out onto a tray. Pat dry with paper towels then sprinkle with salt.
Brown lamb – Heat the oil in a large, heavy-based, oven-proof pot over high heat. Add ⅓ lamb and brown aggressively all over (about 3 minutes). Remove into tray, then repeat with remaining lamb.
Brown onions – Turn the heat down to medium high and add the onions. Cook for 2 minutes stirring regularly until brown all over. Remove into a bowl.
Sauté carrots & garlic – Add the carrot and cook for 2 minutes stirring regularly until it starts to soften. Add garlic and cook for 20 seconds.
Add tomato paste and cook for 1 minute stirring constantly. Add the lamb back in the pot including any juices that are on the tray. Stir to combine.
Stir in the flour and cook for 1 minute.
Pour the wine, stir until the lamb is coated in a pale red, loose paste then add the stock and stir gently until combined.
Add salt, pepper, thyme and bay leaves and stir well.
Bring to a simmer, then cover and transfer to oven for 1 hour.
Remove from the oven, stir in potato, turnip and onions. Submerge ingredients as best as you can.
Cover with lid and return to the oven for 1 ½ hours, or until the lamb is 'fall-apart tender'.
Add the frozen peas, stir VERY gently using a rubber spatula, cover and leave it for 2 minutes.
Remove from oven, taste sauce and add salt if needed.
Serve hot with some warm crusty bread to soak up all that beautiful sauce!
