Heat oven to 350 degrees. Grease 13x9x2-inch baking pan.
Combine flour and brown sugar in a large mixing bowl. Cut in butter until mixture resembles coarse crumbs.
Add egg and blend well with a stand or hand mixer. Stir in 1 - 1/2 cups chocolate chips and nuts. Set aside 1 - 1/2 cups of the mixture.
Press remaining crumb mixture onto bottom of prepared pan. Bake for 10 minutes.
Remove from oven and immediately pour sweetened condensed milk evenly over hot crust.
Top with 1 - 1/2 cups toffee bits.
Sprinkle reserved crumb mixture and remaining 1/2 cup chips over top.
Bake 25 to 30 minutes or until golden brown. Sprinkle with remaining 1/4 cup toffee bits. Cool completely in pan. Cut into bars. Top with vanilla ice cream and you'll be in heaven.