Instructions

Whisk flour, cornstarch, and salt in bowl; set aside. With electric mixer on medium-high speed, beat butter, sugars, and vanilla until smooth, about 1 minute. Reduce speed to low; add flour mixture, chocolate, pecans, and toffee; mix until dough forms, about 1 minute. Gather dough, wrap in plastic, and refrigerate until firm, at least 1 hour or up to 3 days.
Adjust oven racks to upper-middle and lower-middle positions and heat oven to 350 degrees. Line 2 baking sheets with parchment paper. On lightly floured work surface, roll half of dough into 11-inch circle, about 1/4 inch thick. Using 3-inch star-shaped cookie cutter, cut out cookies, gathering and rerolling dough as necessary. Place cookies 1 inch apart on prepared baking sheets and bake until edges are golden brown, 12 to 14 minutes, switching and rotating sheets halfway through baking. Let cool 10 minutes on baking sheets, then transfer to wire rack and cool completely. Repeat with remaining dough. (Cookies can be stored in airtight container at room temperature for up to 1 week.)