Melt butter in a non-stick skillet or saucepan over medium heat.
¼ cup butter
Stir in the flour.
¼ cup all-purpose flour
Cook until the mixture is golden in color (about 5 to 7 minutes), stirring constantly. (You want it to bubble gently. If it is bubbling too vigorously, turn the heat down to medium-low.)
Slowly whisk in the broth, about ¼ cup at a time, until smooth. Bring to a simmer.
2 cups beef broth
Lower the heat to medium-low and simmer until thickened, about 2 to 3 minutes, stirring occasionally.
Stir in dry sherry, if using.
1-2 tablespoons dry sherry
Season with salt and pepper, to taste. Add some fresh herbs, if desired.