1/2 cup butter, softened
1 cup brown sugar
1/2 cup white sugar
1 egg, beaten
1 teaspoon vanilla extract
In a large saucepan over medium heat, mix together butter and brown sugar. Add egg and vanilla and mix together. Bring mixture to a boil, stirring constantly, and reduce heat to low. Reduce heat to low and boil gently for about 10 minutes, stirring occasionally, until mixture is thickened. Cool completely.
Spread prepared dough into the bottom of a microwave-safe bowl and place in microwave. Microwave at 10 to 12 minutes, stirring constantly, until well chilled. Roll out onto a piece of waxed paper. Cut out a circle about 1/4 inch thick. Cover cookies and place on waxed paper. Refrigerate 8 hours or overnight.
When ready to use, roll the dough out to 1/4 inch thickness. Place filled cookies 2 inches apart onto open parchment. Cover and refrigerate overnight. While cookies are still warm, place and egg in large bowl. Mix thoroughly and roll out to 1/4 inch thickness. Cut into 6 slices. Serve warm or cold, or both.