Pureeing food requires equipment that liquefies, such as a blender or immersion blender. Meat and vegetables must be cooked first, typically steamed. Fruits do not require pre-cooking. Almost everything require the addition of water or broth to thin the mixture enough for pureeing.
Blenders and immersion blenders are the only products that turn ingredients into a true, smooth-textured puree. Food processors or food mills tend to leave chunkier or grittier textures. If you want to puree hot ingredients such as soup or freshly cooked vegetables, the immersion blender is the safest option. Immersion blenders, also called stick blenders, puree the ingredients in the pot in which the ingredients are cooked. Blenders require pouring the ingredients into the blending container. Burns can result when pouring hot ingredients into a blender.
Liquids must usually be added to the ingredients to blending them into a puree. Some fruits may be juicy enough on their own and not require extra liquid. Pureeing items such as meats requires a substantial amount of liquid and very tender meat. Recipes typically list the amount of liquid needed. If you're not using a recipe, put your ingredients in the blender, add a small amount of liquid, and turn the blender on. Small amounts of liquid can be continually added until the desired consistency is reached.