Pound chicken breasts flat and place on a plate. Keeping the pounded side up, place one breast with one of its short sides facing you on a board.
Grind a little black pepper and cayenne pepper on the chicken, then put one slice of mozzarella and four sage leaves lengthways in the centre.
Starting at the short end nearest to you, roll the chicken away from you into a sausage shape with the cheese enclosed in the centre.
Put the roll on a plate and repeat with the remaining chicken and cheese.
Melt oil and butter in a large frying pan over a medium to high heat until foaming.
Lay rolls in the pan, cook for 3 minutes, then turn them over and cook a further 3 minutes. Reduce heat slightly if the butter turns brown. Baste by spooning juices over the chicken with a metal spoon.
Repeat on the other two sides, then cook for a further 3 minutes, basting the ends of the rolls. Total cooking time should be about 15 minutes. Remove rolls with a slotted spoon and keep warm.
Pour fresh cream into pan, increase heat to high and stir vigorously with a wooden spoon as the cream sizzles. Scrape spoon over bottom and around sides of pan to dislodge any bits of sediment. This is called ôdeglazingö and takes a minute or so. Pour over the chicken.
Leave chicken rolls whole or slice neatly, and arrange on a platter with boiled baby potatoes and patty pans.