Fregola—the golden toasted Sardinian pasta—is a favorite ingredient to slip into bouillon-based long-simmered soups to add body and texture.
Simmering is a method of cooking using water or a flavored liquid heated to around 180° to 185°F (82° to 85°C), just under boiling (212°F/100°C); you should see a few bubbles rising to the top here and there. Using a lower simmering temperature can sometimes involve long cooking times, allowing for an exchange of flavors between the ingredient and the flavored liquid, which is often included as part of the final dish. Simmering is an excellent technique for tenderizing tough cuts of meat or cooking vegetables for a long time to draw out more flavor, such as with soups.
Cooking fish, poultry, or meat at a temperature any higher than a simmer is not advisable, as it will toughen and dry out the flesh and can damage the food as it is pushed around the pot by the bubbles.
Tips
• To achieve an even simmer, use a heavy-duty pot that will distribute the heat evenly.
• Place the pan of liquid over high heat, and when the liquid comes to a boil, reduce the heat to its lowest setting, so that the liquid calms down to a gentle simmer, with just a few bubbles rising to the top.
• If your lowest gas or electric cooktop settings are too hot to achieve a gentle simmer, you can invest in a heat diffuser, a relatively compact kitchen tool that diffuses the heat coming from the heating element to lower the temperature under the pan if the heat source is too hot. These are often sold as “flame tamers” or under the brand name SimmerMat—both do the same thing. Look for diffusers made from quality material such as steel or cast iron, which will distribute heat evenly.
• For dishes that you plan to simmer for a long time, use a large pot that will hold enough water to keep the food submerged for the duration of the cooking time as water evaporates. For dishes that have a short cooking time or require less water, a small pot will do.
• A skillet or shallow pan works best with delicate foods that may crumble easily. Fish and chicken can be plunged into boiling water (blanched) for 30 seconds to 1 minute, to freshen the ingredients and remove any unwanted strong odors.
• A baking parchment lid (see below) sits on top of the water and has several useful functions: to keep the food submerged for even cooking; to prevent delicate food from being tossed about by the bubbles; and to help increase the cooking time and concentrate flavors.
Baking Parchment Lids 
Wooden Japanese drop lids, which come in several sizes and are designed to snugly but very delicately float on the liquid surface inside a pot, are ideal for using with simmered dishes. They are expensive and hard to come by, however, so making a baking parchment lid is a useful alternative.
Measure a length of baking parchment slightly larger than the diameter of the pot you are going to simmer in. Fold the piece of parchment in half on the diagonal to make a triangle. Fold the triangle in half again along the closed edge. Continue to fold the paper in half three more times, always using the closed folded corner as the pivot for the fold. Holding the pointed end of the folded paper measure at the center of the pot with the wide end toward the outer edge, use a pair of scissors to cut the wide end in a softly rounded arc following the curve of the pot. Snip off about 1 inch (2.5 cm) from the pointed end to create a steam vent. Unfold the paper and you should have a circular paper lid perfectly sized to the surface area of your pot.