Melt butter and add in the chopped shallots and garlic. when fragrant add in the mushrooms
Add in the red wine. Reduce to half by boiling before adding the beef stock.
After adding the beef stock let it reduced to half by boiling.
Add the roux slowly and stir till it reach the consistence you want.
When done, add in any excess juice from your beef SousVide and a slice of butter for a glossy jus.