Preheat oven to 350.
Combine flour, sugar and cocoa, cut in butter until crumbly.
Add egg; mix until well blended. Add vanilla extract.
Reserve 1 1/2 cups crumb mixture.
Press remainder evenly on bottom of greased
13x9" baking pan.
Bake 10 minutes.
In saucepan, combine sweetened condensed milk and 1 cup chocolate chips.
Over low heat, cook and stir until chips melt and mixture is smooth.
Spread evenly over prepared crust.
Add nuts and remaining 1 cup chocolate chips to reserved crumb mixture; sprinkle evenly over top.
Bake 25-30 minutes or until center is set.
Cut into bars.
Store covered at room temperature.