Chocolate Chip Toffee Bars

I found this recipe a very long time ago, altered it slightly, and have been making it every year at Christmas. It's one of my most favorite cookie recipes. 

2-1/3 c all-purpose flour
2/3 c packed light brown sugar
1-1/2 sticks unsalted butter
1 egg, slightly beaten
12-oz package semi-sweet chocolate chips
1 c coarsely chopped nuts (I use pecans)
1 can (12 oz) sweetened condensed milk
1-3/4 c English toffee bits (I use Heath bars, chopped up in my food processor)

Preheat oven: 350*. Grease 13x9x2" baking pan (glass or metal). In a small bowl, combine the chocolate chips and nuts; set aside. In a large bowl, stir flour, brown sugar. Cut in butter with pastry knife until mixture resembles course crumbs. Add egg, mix well. Stir in 1-1/c of the chip-nut mixture. This will be the crust mixture. Reserve 1-1/2 c of the crust mixture in a small bowl; set aside.

Press remaining crust mixture onto the bottom of the baking dish, trying to get it spread evenly on the bottom. Bake for 10 minutes. 

Pull out of oven, pour the sweetened condensed milk evenly over hot crust. Top with 1-1/2 c toffee bits. Sprinkle reserved crust mixture and remaining chip-nut mixture over top. Bake 25-30 minutes or until golden brown. 

Pull out of oven, sprinkle remaining toffee bits on top. Cool completely. Cut into bars. Makes about 36 bars, depending on how big you cut them. When storing them, make sure you put a sheet of waxed paper between each layer of cookies.