Line a 9-in. baking pan with foil and grease the foil; set aside.
In a large bowl, combine flour and sugar. Cut in butter until mixture resembles coarse crumbs. Press into prepared pan; prick crust with a fork. Bake at 350° for 18-22 minutes or until set and edges begin to brown.
Immediately sprinkle with chocolate chips. Allow chips to soften for a few minutes, then spread over crust; set aside.
In a large heavy skillet over medium-low heat, cook sugar until melted. Do not stir. Reduce heat to low; cook for 5 minutes or until golden brown.
In a large saucepan, combine the butter, cream and corn syrup. Slowly pour in cooked sugar. Cook and stir over medium heat until a candy thermometer reads 240° (soft-ball stage). Remove from the heat; stir in walnuts. Pour over prepared crust.
In a microwave, melt chocolate; stir until smooth. Drizzle over caramel layer. Cover and refrigerate for 2 hours or until firm.
Using foil, lift candy out of pan. Gently peel off foil; cut candy into squares.
We recommend that you test your candy thermometer before each use by bringing water to a boil; the thermometer should read 212°. Adjust your recipe temperature up or down based on your test.