This gluten-free red wine & porcini jus is thickened with cornstarch rather than the traditional roux-based gravy method using plain flour.  This involves a different but, in fact, easier cooking method.  Basically, you first make the base liquid flavoured to your liking then you thicken that liquid with cornstarch (or arrowroot) mixed with a little water.  It’s very easy but you need to be aware of the rules for cooking with cornstarch! (see below)