Heat the oil in a large pan over a high heat and brown the chicken pieces all over until golden (you will need to do this in batches). Remove from the pan, drain off most of the fat and set aside.
Add the garlic, shallots, sundried tomatoes and chopped peppers to the pan. Cook for a further 10 minutes over a medium heat. Add the tinned tomatoes, chicken stock, Worcestershire sauce and rosemary, stir, then return the chicken pieces to the pan. Bring to the boil and cook for a further 20 minutes, adding the olives 5 minutes before the end of cooking.
Meanwhile, preheat the oven to 200°C, fan 180°C, gas 6. Mix the grated potato with the flour and mustard powder, then season well. Form the mixture into 8 similarly sized balls, place them on an oiled non-stick baking sheet, brush the tops with oil and bake in the oven for 20-30 minutes. Serve the stew with the hash browns and green beans.