This all-purpose pan sauce owes its light consistency to a simple technique: adding stock to the drippings in a frying or roasting pan and then simmering until full flavored and slightly thickened. A few spoonfuls will dramatically enhance a dish.
Degrease the pan drippings
Evaluate the pan drippings and darken them if necessary by cooking over high heat for a minute or two. Pour the drippings from the pan into a fat separator and let stand for a few minutes until the fat rises to the top. Alternatively, you can pour the drippings into a heat-proof measuring cup instead, let stand, then use a soup spoon to skim the fat off the top. Pour the juices into a large glass measuring cup, leaving the fat behind.
Replenish the pan juices
Choose beef or chicken stock to match the food you cooked, or follow your recipe. Add enough stock to the degreased pan juices in the measuring cup to make a total of 1 ½ cups.
Saute the shallots
Return the pan with the browned bits in the bottom to the stove and place over high heat, using 2 burners if you used a roasting pan. Add 2 tablespoons of butter and heat until until the butter melts and the browned bits are sizzling. Add a finely minced shallot and cook, stirring, until the shallot softens and becomes translucent, about 1 minute.
Deglaze the pan
Pour the stock-juice mixture into the pan and bring to a boil, scraping up the browned bits no the bottom and sides of the pan with a wooden spoon. These browned bits will add a rich flavor to the final sauce.
Reduce the sauce
Once the liquid has absorbed the browned bits, let the sauce boil until it has reduced to about 1 cup; this should take about 3 minutes, depending on the size of the pan. Tilt the pan occasionally to estimate the amount of liquid remaining in the bottom.
Thicken the sauce, if desired
If you’d like the sauce to be thicker, or if your recipe calls for it, use a cornstarch slurry. Combine 1 ½ teaspoons cornstarch and 2 tablespoons water in a small bowl and stir to blend. Whisk a little of it into the simmering sauce, then bring to a boil just until the sauce thickens; this should take a minute or less.
Finish the sauce with butter
Remove the pan from the heat. Cut 1 tablespoon butter into small cubes. While whisking constantly, drop the butter cubes, 1 or 2 at a time, into the sauce. This technique gives the sauce a slightly thicker body and nice sheen. Stir in salt, pepper and herbs to taste, adjusting the seasonings to your liking.