In large bowl, beat butter with brown sugar. Beat in vanilla and eggs. Stir in flour just until mixed. Fold in chocolate chips. Spoon batter into greased 20 cm square baking dish; bake in preheated 180ºC oven 35 to 40 minutes or until cake tester inserted in centre comes out clean. Cool. Cut into dozen squares. While squares are baking, make sauce. Place butter, sugar and cream in medium saucepan and bring to a boil. Cook, stirring, about 2 minutes. Add vanilla. Cool. Serve brownies with a scoop of ice cream and a drizzle of sauce. Makes dozen servings.