Cooking food in a sealed parchment paper or foil pouch (called en papillote) is a technique embraced by dieters; it's considered healthy because it uses very little fat. This doesn't mean it's flavourless, though. Because the pouch is tightly sealed, it locks in the flavours and prevents them from being diluted. The ingredients should be prepared so they all take the same amount of time to cook. This might mean blanching firm vegetables or cutting them smaller so they cook quickly, before wrapping them up with the other ingredients.
You'll need larger sheets of parchment paper - the standard 30cm (12 inch) packs available in rolls in most supermarkets are too small when trimmed down size to wrap the ingredients. Buy the rolls that are 38cm wide.
Peel the baby carrots and cut in half lengthwise. Trim the ends off the green beans then cut them in half. Bring a pot of salted water to the boil and cook the carrots until they're crisp-tender (three to five minutes). Remove them from the water with a slotted spoon and place in a bowl of iced water to stop them cooking.
Bring the water to the boil again and blanch the string beans for about one minute, until they're crisp-tender. Drain the string beans and put them in the iced water. When the vegetables are cool, drain them and pat them dry.
Halve the cherry tomatoes. Place the carrots, green beans and tomato in a bowl and drizzle with 15ml (1 tbsp) of olive oil and the sake. Grate the lemon zest over the ingredients, add a little salt and pepper and mix well.
Lightly season the fish fillets with salt and pepper. Scrub the clams then rinse and drain them.
Preheat the oven to 220° C (430°F). Take four 45cm by 38cm (27¾ x 15 in) sheets of parchment paper and fold each one in half like a book. Cut each folded sheet so when you open it, it'll be a large, wide heart shape.
Lay the hearts on a flat surface and brush lightly with olive oil on one side. Divide the vegetables and their juices over the heart, placing them close to the seam on the oiled side and making a flat "bed" that's slightly larger than the piece of fish.
Put a piece of fish on top of the vegetables and add four clams to each pile. Lightly drizzle the fish fillets with the remaining 30ml (2 tbsp) of oil, dividing equally over each portion.
Fold the parchment over the ingredients. Starting at the narrow end of the heart, fold up the two layers of parchment and tightly crimp and pleat the entire perimeter to seal in the ingredients.
Place the packets on a baking sheet and bake at for 10 to 12 minutes. Place the packets on dinner plates and serve, cutting them open at the table so the fragrant steam escapes.