Steam marrow until tender. Puree marrow in blender / food processor. Sauté onions in minced garlic in butter until tender. Shred cheddar cheese. Add onions, garlic, cheese, bread crumbs, eggs and herbs to zucchini. Thaw frozen puff pastry 20 minutes. Roll out each sheet on slightly floured board. Divide each sheet into 4 squares. Fill each of the 8 squares with marrow mixture leaving 1-inch border on all sides. Brush border with egg white; prick top with fork. Place pies on cookie sheet and bake in 400°F oven for 30 minutes or till golden brown. Serve warm. See cheese puff pies for frozen puff pastry directions. Yield: @ 8 Pies