Mix together bacon, mushrooms, mayonnaise, and garlic powder; set aside. Separate the crescent rolls into 4 rectangles and press the perforations to seal. Spread the rolls with cream cheese; top with the bacon mixture. Roll lengthwise and slice into 1" pieces. Arrange, flat side down, on an ungreased baking sheet. Brush with beaten egg white and sprinkle lightly with poppy seed. Bake for 9-10 minutes at 375 degrees, or until golden. Makes 3 dozen (9 slices per roll).