- Preheat oven to 450 degrees. Place two baking sheets in the oven so they will be good and hot when it is time to cook the fish.
- You will need a 30-inch piece of kitchen parchment paper per serving. Fold paper in half and make a crease to mark the center, then unfold. Grease paper with butter. Place a fish fillet on one half of paper (we used flounder but this technique is very versatile and you may choose other fish or any ingredients you like). Season with salt and pepper. Sprinkle with a sixth of the sweet pepper. Top with a sixth of the lemon zest. Top with an herb sprig and a bay leaf. Remember that how you arrange it now is how the diner will see it. Sprinkle each piece of fish with a teaspoon of lemon juice and 2 teaspoons vermouth.
- Close the empty half of the paper over the fish as if you were closing a book. Starting at one end of the spine of this book, make small tight overlapping folds all the way around the paper. Take care to use enough paper in the fold so that no steam will be able to escape. The final result will resemble a large turnover made of paper.
- Just before you want to eat, carefully arrange the packets on the hot sheet pans. It usually takes 10−12 minutes for these to cook. They are done when the paper is all puffy and full of steam. Remove each packet to a dinner plate and serve at once with your side accompaniments of choice. A wonderful aroma will be released when they are opened at the table.