Melt the butter in a saucepan and sauté the shallots briefly until translucent (approximately 3 minutes).
Deglaze with the Port and red wines and reduce until most of the wine has cooked off, (approximately 5 – 6 minutes)
Add the demi glace, salt, pepper, bay leaf, and thyme and simmer for approximately 5-6 minutes (or until the sauce has thickened).
Strain the sauce, add the heavy cream (if desired), and return to a simmer for a few minutes and serve.
The optional heavy cream gives the sauce a richer color and additional flavor.