The common garden snail, Helix aspersa, is perfectly edible, once purged of anything poisonous it might have been eating. This simply involves keeping them somewhere where you can control what they eat. I use a large plant pot (so that there is some drainage) with a large stone in it for the snails to clamber over or hide under for shade. You then need to cover the pot with something that keeps the snails in but is well ventilated. I use a plastic mesh packing tray, but fine chicken wire would also do the job. You need to weight this down with stones to prevent your snails escaping as it is amazing what the combined pushing power of a few dozen snails can be. Keep the bucket in a cool shady place and keep some moisture in the bucket. Herbs or lettuce leaves are the usual recommended food although I found they seemed to prefer oats. They should be kept like this for 5 days, although I often wait longer if I haven’t amassed enough snails to be worth cooking. You may however know of some favoured hiding places for them and remember always to look after rain. Just keep them fed and watered and clean them out at least once a week – the easiest way is to pick the snails out into a fresh plant pot and then swill out the dirty pot onto your garden. Don’t feed the snails for 2 days before you want to eat them so that their gut is quite clean.
I have read several very different methods for cooking the snails but the one I favour is as follows:
Bring a large pan of quite heavily salted water to the boil. Put your snails into a colander and rinse them under running water, shaking the colander so that they all retract into their shells. Tip the snails into the boiling water and cook for 10 minutes then drain and rinse again. This stage will kill the snails and rid them of their slime.
Next remove the snails from their shells with a cocktail stick. You will soon get the knack of twisting your wrist as you pull them out. Now simmer them for 3 – 4 hours in a mixture of cider and water flavoured with a few herbs and vegetables.
Meanwhile prepare a herb butter. Allow 250g of butter for 3 dozen snails, which will feed 2-3 people. Add a tablespoon each of chervil, chives, and parsley plus about a teaspoon each of chopped thyme and tarragon leaves. Chop and blend the whole lot in a food processor and season with salt and pepper.
Personally I think it is more trouble than it is worth to put the snails back into their shells for serving but if you do want to serve them this way, chill the butter until firm then put a knob into each shell, followed by the snail and then add another knob of butter to seal them in. Instead I just put them into small ramekins with the butter and then scatter the tops with a mixture of breadcrumbs and grated cheese. These are then put into a very hot oven for 10 minutes, until the top is bubbling, and served turned out onto a slice of toasted bread.