To toast walnuts, spread in a single layer in a 9" glass pie plate. Stirring every 2 minutes, microwave on high 6 minutes or until toasted.

Place butter in a 2 quart glass measure. Microwave on high 1 minute. Blend in brown sugar and condensed milk. Stirring every 2 minutes, microwave on high 8 to 9 minutes or until mixture is a medium caramel color. Stir in vanilla and beat with a wooden spoon for 2 to 3 minutes. Fold in walnuts. Pour into buttered 8" square dish. Cool to lukewarm; then refrigerate until set. Cut into squares. Makes 36 pieces.