To Make Mushroom Filling: Melt 65g butter in a small fry pan over medium heat. Add mushrooms, salt and pepper and saute together, stirring, until mushrooms are dark. Remove fry pan from heat; stir in nutmeg and 3/4 cup breadcrumbs.
Spoon mushroom mixture onto the end of each chicken breast, roll up and fasten with toothpicks. Place seam side down in a lightly greased 22x33 cm baking dish. Brush melted butter over breasts, then sprinkle with remaining 1/4 cup breadcrumbs. Pour cream over all.
Bake uncovered at 180 degrees C for 30 minutes or until chicken is cooked through and no longer pink.