A hearty stew requires a thick soup base to support the tender vegetables and succulent chunks of meat. Although it's possible to simmer the stew until most of the excess liquid evaporates, that requires a long cooking time. Use a roux to thicken a stew at the beginning of preparation, before you have simmered the ingredients. If you need to thicken a pot of prepared but overly thin stew, a slurry provides a quicker option.
Roux the Day
Heat oil, butter or shortening in the bottom of your soup pot over medium heat until it melts and begins to bubble. Use ¼ cup of oil for every two quarts of stew.
Whisk an equal amount of flour into the bubbling oil, adding a small amount at a time so it incorporates completely without clumping. Continue to whisk the mixture for one to two minutes, or until it thickens and begins to bubble.
Stir in the liquid for the stew a little at a time, using the whisk. Continue to add the liquid slowly until it's incorporated with the roux and begins to thicken. Add the remaining stew ingredients and cook as usual.
Place the flour in a glass measuring cup or heat-proof bowl. Use 1 tablespoon of flour for every 1 quart of stew.
Slowly pour 1 cup of liquid from the hot stew into the flour, whisking constantly so the liquid and flour mix thoroughly without lumps.
Whisk the slurry into the remaining stew. Add the slurry slowly so it incorporates without forming lumps.
Heat the stew over medium to medium-high heat, stirring constantly until it reaches the desired thickness.