Pre-heat oven to 385F.

Remove stalks from mushrooms and take Swiss chard leaves off stems. Chop Swiss chard into smaller pieces.

Remove sausages from casings and put sausage meat into a bowl. Add Swiss chard, garlic powder, worcestershire sauce, pepper, salt, parmesan, egg, and thyme (remove leaves from the twigs). Mix using your hands.

Place an equal amount of meat over each mushroom cap (gill side up).

Place mushroom caps onto a non-stick baking sheet. Bake for one hour, or until sausage is cooked.