In a small saucepan, place the red wine, shallots, thyme, and bay leaf and set over medium heat.
Bring the mixture to a rolling boil and continue to cook to reduce the contents to half of the original volume.
Add the beef stock to the pan and bring the mixture up to a boil again.
Skim and discard any foam that appears on top of the sauce using a tablespoon.
Continue cooking the bordelaise until it has thickened enough to coat the back of a spoon—otherwise known as having a nappe consistency. To check, simply dip a tablespoon into the sauce and swirl it around. Lift the spoon and flip it over to look at the back. The sauce should have coated the spoon but if it quickly runs off, it is not yet thick enough and needs to be cooked more.