Slice the shallots, garlic and celery.
Heat the oil in a heavy based casserole dish over low heat and add the chicken. Cook for about 10 minutes over low heat, then add the chopped veggies and the oregano.
Cook for another 10 minutes.
Meanwhile, peel and dice the sweet potatoes, carrot and beets.
When the chicken skin is brown and the veggies are soft, add the chopped root vegetables.
Pour over the tinned tomatoes then, using the tin, add water to cover everything well.
Add the stock cube and season with salt and pepper to your liking.
Bring to the boil. Cover and cook over lower heat for about 35-45 minutes.
If the sauce is not thick enough, take off the lid, turn up the heat and cook until it has reduced to a thick, silky jus.
Serve warm.