Aluminum foil acts as a barrier between boiling water and food, and when wrapped securely, allows the food to steam inside it. Although you can wrap any food in aluminum foil and boil it, you achieve best results with food that allows the foil to conform to it snugly. Foil-wrapping the food before poaching or boiling cooks the food in its own moisture, with the water acting more like a conduit of heat than a cooking liquid.
Prepare the food according to the recipe. This include any scrubbing, peeling or cutting needed for cooking. Place a piece of aluminum foil twice the width and length of the food on the work surface.
Position the food in the center of the foil. Bring the two horizontal edges of the foil together and secure it with several folds. Tuck the two vertical edges of the foil under. Place another piece of foil twice the size of the food on the work surface.
Rotate the wrapped food a quarter turn and place it on the second piece of foil. Again, bring the two horizontal edges together and fold several times to secure the foil. Tuck the other two edges under.
When wrapping the food, remember the goal is to keep the boiling water from touching the food as much as possible.
Do not cook acidic foods, such as tomatoes, in foil. Acetic acid leaches aluminum from foil, adversely affecting the taste, quality and safety of the food.