This is a sauce for a roast chicken, but the process is similar for any pan-fried or roasted meat.
This recipe assumes you have taken your chicken out of the roasting pan and set it aside to rest. Still in your pan are the juices from the meat and the fond (the little caramelized bits), which have a lot of flavour.
½ cup white wine
1 cup chicken stock
a squeeze of fresh lemon
Skim off almost all the fat, or as much as you can.
Over medium-high heat, deglaze the pan by adding the wine and scraping all the brown bits off the bottom.
Once the bottom of the pan is clean and the wine is mostly evaporated, add the chicken stock and reduce by half (8-10 minutes).
Taste and season as necessary. It is also nice to add a bit of lemon juice for some acidity.
To thicken the sauce
Use 1 tablespoon cornstarch mixed with a 1 tablespoon of stock or cold water for each cup of sauce. Add and whisk constantly for about 5 minutes.
If you don't have cornstarch, blend 1 tablespoon unsalted butter and 1 tablespoon flour using a fork and whisk into the sauce until smooth.
Once off the heat, you can whisk or swirl in some butter (about 2 tablespoons). This step is optional, but will give your sauce a glossy appearance and a velvety texture.
Strain the sauce before serving if you want it perfectly smooth.