Created by Mikekey on August 31, 2015
Step 1: Melt 2 tablespoons butter in heavy large skillet over medium-low heat. Add onions and saute until golden and tender, about 12 minutes.
Step 2: Add vinegar and boil until reduced by half, about 1 minute.
Step 3: Add bourbon and broths and boil until slightly thickened, about 10 minutes.
Step 4: Remove from heat and add remaining butter and whisk just until melted. Season with salt and pepper.