Preheat the oven to 180C/350F/Gas 4.
For the cheesy mash, cook the potato in boiling salted water for 7-8 minutes, or until tender. Drain well, then mash together with the cheese and cream and season with salt and freshly ground black pepper. Stir in the chopped parsley.
For the chicken roulade, pile the chopped cheese and garlic in the middle of the opened out chicken breast. Roll up the chicken tightly and tie with kitchen string.
Heat the oil in an ovenproof frying pan, and add the stuffed chicken breast. Fry for 2-3 minutes on all sides, or until golden-brown, then transfer to the oven to roast for 6-8 minutes, or until the chicken is cooked through. Remove from the oven and thickly slice.
To serve, pile the cheesy sweet potato mash onto a serving plate and top with the slices of chicken roulade.