3/4 cup butter, softened
1/2 cup granulated sugar
1 tsp vanilla extract
1 1/2 cups all-purpose flour
1/2 cup + 1/3 cup pistachios, chopped, divided
1/2 cup semi-sweet chocolate chunks
1 beaten egg white
Preheat oven to 300 degrees.
Grease a cookie sheet and set aside.
In mixer bowl, with electric mixer, cream the butter and sugar together until light and fluffy; blend in the vanilla. Gradually add the flour; mix well. Fold in the half cup of pistachios and the chocolate chunks.
Using your hands, pat the dough into an 8 x 10-inch rectangle. Brush with the egg white and sprinkle the third cup of pistachios over the top. Bake at 300 degrees for 35 to 40 minutes until the shortbread is lightly browned. Cool completely before cutting into 20 squares.