Preheat oven to 350°.
Line cookie sheet with parchment paper. (Or spray well with non-stick spray.)
Cover sided cookie sheet (I used 15 1/2" X 10 1/2" jelly roll pan) with single layer of graham crackers, touching each other.
In medium saucepan over medium heat, melt butter.
Stir in brown sugar and bring to a boil to make a caramel syrup.
Pour hot syrup over graham cracker layer.
Sprinkle with coarsely broken walnuts.
Bake for ten minutes at 350°.
Remove from oven.
Cool for 3-5 minutes or until squares begin to harden.
Break apart while still warm.
Use a small spoon (I used a baby spoon) to drizzle melted chocolate over the squares.
Cool completely and store in an airtight container.