Add a splash of veg oil to a small non-stick skillet on medium-high heat. Add the potatoes and fry for 5 minutes until browned and fully cooked. Remove the potatoes and season them lightly with salt and pepper.

Season the chicken with salt and pepper and sear them in the pan for about 10 minutes until browned all over. Spoon the excess oil from the pan and add the onions. Let fry for 1 minute.

Add the chicken stock and thyme to the pan. Let simmer for 30 minutes, turning the chicken over regularly. If the liquid level gets too low, add extra water. You want to keep the chicken about half submerged.

Add the carrots and sage to the pan. Let simmer for 10 minutes. Remove the chicken to a plate and let the sauce reduce until there's only about a cup left in the pan.

Stir the butter into the pan until it melts. Make a slurry by mixing the flour with a few tbsp water, then stir it in also. Turn the heat down to low and let simmer gently for 2 to 3 minutes. Check the seasoning and add extra salt and pepper as needed.

Return the chicken and potatoes to the pan along with the peas. Let simmer a final minute to bring everything up to temperature, then serve.