Line a cookie sheet with nonstick baking paper. Arrange graham squares on the pan.
In a saucepan, heat brown sugar and margarine until boiling. Continue cooking 5 minutes more, stirring constantly. Remove from heat. Add vanilla.
Working quickly, pour caramel over graham squares. Spread evenly. Sprinkle with chopped nuts.
Melt chocolate chips. Drizzle over the nuts. Chill for a few minutes to allow chocolate to set. Serve.
Feeling Expert tip: To test if the brown sugar and margarine has been boiled long enough, drop a bit of the syrup into a small bowl of ice cold water. The drop of syrup should turn into a crisp brittle.