1. Mix the breadcrumbs and 1 tablespoon butter and toast the breadcrumbs in the microwave oven until golden brown, stirring often to prevent burning.
2. Wash and trim the mushrooms and slice thinly. Add the lemon juice, onion, butter, salt and pepper. Cook, covered. 5 minutes in the microwave oven.
3. Heat the cream in the microwave oven in a separate covered dish to just short of the boiling point.
4. Stir the flour into the mushrooms, stirring rapidly to prevent lumping. Stir in a bit of the cream. Stir in each egg yolk separately. Stir in the remaining cream.
5. Cook, covered, in the microwave oven until the sauce is just short of boiling. Sprinkle with the toasted bread crumbs and let stand 5 minutes before serving.
