Which cooking technique uses steam to cook food over boiling water?

The technique that uses steam to cook food over boiling water is steaming. This cooking method involves placing a food item in a steamer basket or on a rack above boiling water, allowing the steam to circulate and cook the food gently. Steaming is often preferred because it retains nutrients and flavors better than some other cooking methods, making it a healthy choice for preparing vegetables, fish, and even certain grains.

In contrast, grilling involves cooking food over direct heat, while roasting is performed in an oven using dry heat, and broiling cooks food with high heat from above. Each of these methods has its own unique approach to applying heat, but they do not utilize steam as the primary cooking method, which is what distinguishes steaming as the correct answer.