Step 1

Adjust the oven rack to the middle position and preheat to 375 degrees F. Line 3 baking sheets with foil.

Step 2

Whisk together the flour, cinnamon, salt and baking soda in a medium bowl.

Step 3

Add the butter to the bowl of a stand mixer fitted with a paddle attachment (or a large bowl if using a hand mixer). Beat on medium-high speed until fluffy, about 2 minutes. Add the granulated sugar and brown sugar and beat on medium-high speed until pale and fluffy, about 4 minutes. Add the egg and beat until combined.

Step 4

With the mixer on low speed, gradually add the dry ingredients. Beat on low until just combined. Add the chopped chocolate toffee bars and pecans and stir to combine.

Step 5

Use a 1/3 cup measuring cup to scoop leveled mounds of cookie dough evenly spaced on the prepared baking sheets. Roll each mound into a ball. Transfer 1 baking sheet to the freezer and freeze until firm, about 20 minutes.

Step 6

Transfer the frozen baking sheet to the oven (meanwhile, transfer the second baking sheet to the freezer) and bake until the edges have melted and the center is still domed, about 10 minutes. Remove the sheet from the oven and bang it firmly on a work surface until a small ripple forms around the outer edge. Return it to the oven and bake until the center puffs up, 3 to 4 minutes. Remove the sheet from the oven and bang it again firmly on a work surface until the edges are rippled and golden brown and the center is soft. Let the cookies cool on the baking sheets, about 10 minutes. Transfer to a wire rack to cool completely. Repeat with the remaining baking sheets, freezing the third baking sheet for 20 minutes while the second baking sheet is in the oven.