Split the fillets or escalopes in half through the centre with a sharp knife to give 8 thin slices. Season the turkey with salt and pepper. Heat butter or margarine and oil in a pan until melted, then fry the turkey for 3 - 4 minutes each side until golden brown. Remove from the pan. Fry the onion and pepper in the same fat until soft and lightly coloured. Stir in the flour and cook for 1 minute, then gradually add the lager and stock and bring up to the boil. Add thyme, sugar and seasonings. Replace the turkey and simmer for about 8-10 minutes until tender. Stir in the cream, adjust the seasonings and reheat gently. Serve sprinkled with chopped parsley.