Meanwhile, heat 1 tablespoon butter in large nonstick skillet over medium heat until melted. Add mushrooms; cook and stir 4 to 5 minutes or until mushrooms begin to brown. Add remaining clove garlic; cook and stir 30 to 45 seconds or until fragrant. Add all but 2 tablespoons beef broth and remaining beer to skillet, stirring until browned bits attached to bottom of pan are dissolved. Bring to a boil; cook 13 to 15 minutes or until mixture is reduced to 1-1/2 cups. Combine remaining 2 tablespoons beef broth and cornstarch; stir into mushroom mixture. Bring to a boil; cook 1 to 2 minutes or until sauce thickens, stirring constantly. Remove from heat; add remaining 1 tablespoon butter, stirring until melted. Season with salt, as desired.