What to buy: Skor or Heath bars, which can be found at most grocery stores, work best in these cookies.
Special equipment: A 3-tablespoon ice cream scoop such as this one makes quick work of assembling these sandwiches. If you don’t have one, you can use a larger or smaller scoop or a spoon, but watch for fast-melting ice cream and don’t overstuff the sandwiches.
Game plan: Using this recipe as your guide, dabble with other colors, textures, and flavors. Use different ice creams, drizzle the edible pucks with caramel or ganache, roll the edges in toasted nuts, coconut, or toffee, or slather the ice cream sandwiches with marshmallow or Nutella. Make minisandwiches for one-bite party treats. If you have leftovers, store them in the freezer in an airtight container for up to 1 week.
The cookie dough can be made 24 hours in advance and stored in the fridge. It can also be stored in a resealable plastic bag in the freezer for up to 2 months. In either case, allow the dough to come to room temperature before baking.
1Heat the oven to 350°F and arrange a rack in the middle. Line a baking sheet with parchment paper; set aside.
2Combine flour, cocoa powder, baking soda, and salt in a medium bowl and whisk to aerate and break up any lumps; set aside.
3Combine butter and sugars in the bowl of a stand mixer fitted with a paddle attachment. Mix on medium speed until light in color and fluffy, about 3 to 4 minutes. Stop the mixer and, using a rubber spatula, scrape down the sides and bottom of the bowl. Add egg and vanilla, return the mixer to medium speed, and mix until smooth, about 1 minute.
4Reduce speed to low, add reserved flour mixture, and mix just until the dough comes together. Add toffee and pecan pieces and mix until they are evenly distributed.
5Scoop dough by rounded tablespoons, placing them 1 inch apart on the prepared baking sheet. Bake until cookies are set around the edges but still soft in the center, about 9 to 11 minutes.
6Remove from the oven and let cool to room temperature before removing cookies from the baking sheet, about 10 to 15 minutes. Repeat with remaining dough (you should have 24 cookies when you’re done).
1Using a 3-tablespoon or 1-1/2-ounce ice cream scooper and working with 6 cookies at a time (3 bottoms and 3 tops), top each bottom cookie with 1 scoop of ice cream and 1 cookie. Firmly press the cookies together to evenly disperse the ice cream in the center (be careful not to break the cookies). Immediately wrap each sandwich with plastic wrap and place in the freezer. Repeat with remaining cookies and ice cream.