Stir in baking soda and vanilla (mixture will bubble). Immediately pour into pan, spreading to 1/4-inch thickness with lightly greased spatula. Sprinkle toffee bits and chocolate chips over top. Let stand 10 minutes or until chips are melted. With spatula, spread melted chocolate evenly over brittle. Cool completely. Refrigerate 20 minutes to set chocolate. Break into 1 1/2- to 2-inch pieces.