Return the saucepan to the stove, add the butter and melt it over medium heat. Add the shallots and cook, stirring often, for 2 to 3 minutes, until softened. Add the garlic and thyme, and cook for 1 minute. Sprinkle in the flour and cook for 1-2 minutes, stirring constantly. Add the warm broth, whiskey (if using), tamari, miso, and pepper. Stir, then bring to a boil over high heat. Reduce the heat to medium and cook for 5 minutes, stirring often.