
(OPTIONAL STEP): Season chicken with salt and pepper. Heat a small amount of oil in a large pan. Sear skin-side down (if using skin on thigh) for 3 minutes, until deep golden brown. Rotate and sear the other side for a further 3 minutes.
Arrange the potatoes in a slow cooker bowl in a single layer. Place the chicken over the potatoes and add the rest of the ingredients over the chicken (except olives and mushrooms).
Add in the mushrooms and olives in the last 30 minutes of cooking. Season with extra salt, to taste and serve.
Substitute crushed/diced tomatoes for the tomato puree if you can't find it.