In a medium bowl, stir together 1/2 cup melted butter, 1-1/2 cups of the cracker crumbs, and 3/4 cup of the toffee bits. Press the mixture evenly in the bottom of a greased/sprayed 9x13x2" baking pan. Refrigerate for 15 minutes or until firm. For an even firmer bar, refrigerate 30 minutes more.
Meanwhile, let the cookie dough stand at room temperature for 10 minutes to soften. In a 2-qt. saucepan heat the chocolate chips, milk, and 1 Tbsp. butter over medium heat, stirring frequently until chips are melted and mixture is smooth. Remove from heat and stir in vanilla. Spread the mixture over the graham cracker crust.
In a medium bowl, break up the cookie dough and mix in remaining 1/2 cup cracker crumbs with wooden spoon until well blended. Crumble mixture evenly over chocolate layer. Sprinkle with remaining 3/4 cup toffee bits.
In a preheated 350-degree oven, bake for 25 to 35 minutes or until golden brown. Cool completely for about 2 hours.