Bake-When-You're-Craving Chocolate Toffee Cookies

In large bowl, beat butter with sugar until fluffy; beat in egg and vanilla.

In separate bowl, sift together flour, cocoa powder, baking powder and salt ; stir into butter mixture in 2 additions. Stir in toffee bits.

Divide dough into quarters; between 2 sheets of waxed paper, roll each into log about 8 inches (20 cm) long. Wrap with plastic wrap and refrigerate, rerolling 2 or 3 times to keep round shape, for 4 hours. (Make-ahead: Refrigerate for up to 3 days or freeze in airtight container for up to 1 month. Thaw in refrigerator.)

Let stand at room temperature for 20 minutes. With sharp knife, cut into 1/4-inch (5 mm) thick slices; place 2 inches (5 cm) apart on parchment paper-lined rimless baking sheets.

Bake in centre of 375°F (190°C) oven until edges are firm, about 10 minutes. Immediately transfer to rack; let cool. (Make-ahead: Layer between waxed paper in airtight container; store at room temperature for up to 1 week or freeze for up to 1 month.)