In a small bowl mix together the flour and brown sugar to make the dough. With fingers, work in softened butter until dough begins to hold together. Press into bottom of 9-inch square pan. Bake at 350 F for 12 to 15 minutes until firm. In another bowl, lightly beat remaining ingredients. Pour over baked crust. Bake 25 minutes or until edges are light brown. Cool and cut into bars.