4 Tbsp. salted butter, divided
2 shallots, minced
2 cups sliced oyster mushrooms
2 cups sliced shiitake mushrooms
1 Tbsp. minced fresh thyme leaves (no stems)
Kosher salt and freshly ground black pepper to taste
3¼ cups low-sodium chicken stock, divided
2 Tbsp. all-purpose flour
2 Tbsp. Angostura bitters
• In a saucepan over medium heat, melt 2 tablespoons butter. Add the shallots and saute until translucent. Add the mushrooms, thyme and salt and pepper to taste.
• When the mushrooms begin to release their liquid (about 3 minutes), add ½ cup chicken stock. Immediately increase the heat to medium-high. When the liquid begins to reduce, add another ½ cup stock. Let simmer 5 to 7 minutes, until the mushrooms have softened, adding an additional ¼ cup stock, if needed.
• In a small bowl, make a paste by combining the remaining 2 tablespoons butter with the flour. Add the paste, along with the remaining 2 cups chicken stock, to the saucepan.
• Bring the sauce back to a simmer and add the bitters. Season to taste. Decrease heat to low and simmer 20 minutes, until reduced by half.