Use an electric mixer to beat together the brown sugar, butter, and flour in a medium sized bowl until well blended. Press crust mixture into the bottom of a lined or greased 8x8" baking pan. Bake in a preheated 350℉ oven for 25 minutes or until lightly golden brown.
While crust is cooling, place sweetened condensed milk and butter in a medium pot. Heat on the stove top at medium-low heat for 5 - 10 minutes, stirring constantly. Pour over cooled crust and use spread evenly with a spoon or spatula.
Bake uncovered in a preheated 350℉ oven for 15 minutes. Sprinkle chocolate chips over the top and continue baking an additional 2 - 3 minutes. Remove from oven and use a spatula to spread the chocolate into an even layer.
Top with toffee bits, then gently press the toffee bits into the mixture before the chocolate has set. Allow to cool completely before slicing into 12 equally sized bars.
Notes
Calories are automatically generated. For best results calculate based on your exact ingredients.