LEGO® The Lord of the Rings™

The first cooking puzzle is found at the start of the Weathertop level during your intial story playthrough and requires making a pan of food.

The second can be unlocked by playing the Amon Hen level in freeplay. It is the second stage of the level on the beach, after the stealth section with Frodo and Boromir. The actual puzzle is just the same as the first and requites finding a fish, an egg and a tomato and placing them all on the same slot as Sam's frying pan. Once all the items are collected using the frying pan on the fire will cause the dead warrior to leap off the chest and unlock the arrow helmet treasure.

Fish - Far left of the beach. Use Shagrat to pull the orange bar then dig with Sam.
Egg - Far right of the beach. Use Sam to dig in front of the Morgul block.
Tomato - Behind the campfire. Use Sam to climb the pillar and attack the plant.

You can unlock the achievement by completing any combination of the two puzzles - Weathertop story, Weathertop freeplay and Amon Hen freeplay.