Traditional chicken jus gras (the inspiration for this recipe) requires roasting chicken bones until golden brown, deglazing the pan with wine, and then adding water (or broth) and simmering for hours until you have a richly flavored stock. Then you strain and reduce that stock down, down, dowwwwn until it’s thick and gelatinous. Then you emulsify in fat (typically rendered chicken or duck fat—YUM!—but also sometimes butter or infused oil).
We took the concept and sped it up, saving all of the deliciousness plus a ton of time. Gelatin imparts the same mouthfeel given by that drawn-out roast and reduction. Xanthan gum stabilizes the jus and thickens it ever so slightly.