Toffee Chocolate Chip Bars

Sticky, tasty goodness. I first tried these when our friend Kana made them.

2 1/3 c. flour
2/3 c. packed light brown sugar
3/4 c. butter, slightly softened, but not at all melted
1 egg, slightly beaten
12 oz. chocolate chips, divided
1 c. coarsely chopped nuts (optional)
1 can (14 oz.) sweetened condensed milk
10 oz. package Skor or Heath toffee bits, divided

Heat oven to 350 degrees. Combine flour and brown sugar in large bowl. Cut in butter until mixture resembles coarse crumbs. Add egg; mix well. Stir in 1 1/2 c. chocolate chips and nuts; set aside 1 1/2 cups of the mixture. Press remaining crumb mixture onto bottom of greased 9x13 pan. Bake 10 minutes. 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 chocolate chips over the top. Bake 25-30 minutes or until golden brown. Sprinkle with remaining 1/4 cup toffee bits. Cool completely (I sometimes ignore this and eat one warm, but my husband prefers them cooled). Cut into bars.