1Heat oven to 350°F. Grease 13x9-inch pan with shortening. Sprinkle bottom of pan with sugar; tap out excess.
2In large bowl, beat condensed milk and peanut butter with electric mixer on medium speed until creamy. Add Bisquick mix and vanilla; beat on low speed until blended. Stir in 1/2 cup of the toffee bits. Press in pan.
3Bake 16 to 18 minutes or until very light brown (crust will be soft). Immediately sprinkle chopped chocolate evenly over hot bars. Let stand 5 minutes to soften; gently spread chocolate with spatula. Sprinkle with remaining 1/2 cup toffee bits. Refrigerate until set, about 1 hour. Cut into 6 rows by 4 rows. Store tightly covered at room temperature.