Hershey Bar Christmas Cookies

1 cup butter
1 cup brown sugar (packed)
1 egg
1 teaspoon vanilla extract
2 cups all-purpose flour
8 (1.55 ounce) chocolate bars
1/2 to 1 cup nuts, chopped

Cream butter and brown sugar together. Add egg, vanilla extract and flour. Spread into a 15 x 10-inch jellyroll pan.

Bake at 350 degrees F for 15 to 20 minutes. Remove from oven and lay chocolate bars evenly over the top while still hot. Let chocolate bars melt and spread over top. Sprinkle with chopped nuts, and cut into small squares.