You'd probably have to simmer it uncovered for another 15 minutes to thicken it up a bit though! (crazyvegankitchen.com)
If you do use soy milk I think adding a bit of cornstarch to a small amount of the milk and then adding to the sauce would help thicken it up a bit. (avocadopesto.com)
The final step of these sliders is simply taking the meat out of the dutch oven, pureeing the broth and onion mixture, and then thickening it up a bit with cornstarch. (greensnchocolate.com)