Strain pan juices and solids into measuring cup (skim of as much fat as you like). Add enough broth to make up to 4 cups.
In a large skillet melt butter, then add flour and cook for 3-5 minutes over low heat, stirring often (this is called a 'roux').
Whisk in the stock a little at a time, then add in the thyme.
Continue simmering until gravy is thickened, stirring often.
Just before serving, add the vinegar, and adjust to taste with salt and pepper.
Notes
*if you are boiling potatoes for your dinner, save the water and use it instead of the chicken broth. The starch in the water acts as a natural thickener.