Cook chicken in boiling sated water til tender. Drain, reserving broth. Remove skin and bones and dice meat finely. Wash and dry mushrooms. Remove, finely chop and reserve stems.
Sprinkle mushroom caps with lemon juice. Melt butter and add stems and garlic and cook 10 minutes, stirring now and then. add 2 or 3 Tbsp. reserved chicken broth and parsley. Season to taste with salt and pepper
Add chicken and egg yolk and mix well. Spoon stuffing into mushroom cavities. Arrange on lightly greased baking sheet and sprinkle with bread crumbs. Bake at 350 for 15 to 20 minutes. Serve hot. Makes 6 servings.