Beef bourguinion needs more sauce.

Sounds like you over-reduced the braise, or didn't start with enough liquid. Add brown chicken stock, or double-stock (when you make stock using stock instead of plain water). You of course COULD reduce a braising liquid to the point it was demi-glace, but that would be missing the point of the dish. Long story, short -- keep strong stock around for circumstances just like this. I like a strong chicken stock to rectify the problem you've had, even though it's a beef dish. Braises are far, far from 'automatic' and can give even world-class chefs headaches.

I’m not sure you can.

The sauce is tasty due to its long cooking of several ingredients. You’ve built layers of flavors and I think adding anything at all is going to dilute that flavor.