Which method of cooking involves food being submerged in a liquid at just below boiling point?

The method of cooking that involves food being submerged in a liquid at just below boiling point is simmering. This technique is characterized by small bubbles forming on the surface of the cooking liquid, but it does not reach a rolling boil. Simmering is ideal for cooking delicate items, such as fish or vegetables, as it allows for a gentle cooking process that helps retain moisture and flavor without breaking down the food's texture.

In contrast, other methods differ significantly in their approaches. For instance, boiling involves cooking food in liquid at a full rolling boil, which is hotter than simmering and can lead to a change in texture and moisture loss, especially in delicate ingredients. Steaming uses the steam generated from boiling water to cook food, allowing it to retain its nutrients and moisture while avoiding direct contact with water. Poaching, while similar in that it also involves cooking in liquid, usually takes place at even lower temperatures where the liquid is just heated enough to maintain a delicate, gentle process, typically around 160°F to 180°F (71°C to 82°C).

Thus, simmering is specifically defined by its temperature range, making it the correct answer for the method of cooking described in the question.