1. Asparagus - Break or cut woody ends off asparagus (woody ends will break of naturally), then cut in half.
2. Cooling the sauce thickens it (because of the butter) so when you pour it over the prawns, it coats it more thickly. That way when you open the packet, there is cream sauce on the prawns. But it is fine to skip the cooling because you will want to squidge the prawns in the cream sauce pooled at the bottom of the foil packet anyway!
3. Heavy duty foil is available at supermarkets and it is slightly thicker than normal foil. It is insurance to avoid the foil packet from leaking. You could use paper inside the foil if baking, or a double layer of foil. Or live dangerously and risk it with a single piece of normal foil! Do not use paper if cooking this on the BBQ - it will burn.
4. Raw prawns hang straight, cooked prawns form a "C" shape, overcooked prawns curl tightly into an "O" shape. Take a peek to ensure prawns are cooked - they should not be translucent, they should be opaque.
5. OTHER VEGGIE IDEAS: Anything that will cook in 10 minutes inside the foil. Thinly sliced carrots, frozen corn or peas (thaw them so they don't bring down the temp of the packet), broccoli (split in half lengthwise), finely sliced fennel, onion, baby or normal spinach (bunch them up on one side), pumpkin or sweet potato instead of normal potato (cook them per recipe), green beans, quartered brussel sprouts.
6. Nutrition assuming 2 tbsp butter and 3/4 cup cheese is used.