Simple but important ..
Preheat oven ( 180 - 200 °C )
Then take bag of snails from the freezer and empty directly into a small oven proof dish... ideally just big enough to fit the portion of snails into with the butter side up. This will make for better eating as butter is kept together and not over cooked, to mop up later with some fresh bread.
Once oven is hot ... place the dish in the top and cook for 10 mins above 80 °C . Watch them near the end when the butter starts boiling away you are ready to take them out the oven.
Now ... ready to serve , you may want to sprinkle some freshly chopped parsley and add a thin slice of butter over the top for presentation.
It's that simple .. a great dish in minutes ..