Grease a 9×13-inch pan and set aside.

In a large pot, melt butter, corn syrup, chocolate chips, and 4 cups of the marshmallows over low heat. Stir until smooth.

Remove from heat and stir in vanilla.

Gently fold in Golden Grahams and remaining 1 cup of marshmallows.

Press mixture evenly into the prepared pan (use wax paper or lightly buttered hands).

Let cool, then cut into squares and enjoy!