Cookie Dough:

In a large mixing bowl, sieve flour, cocoa powder, baking soda, and salt, and whisk to combine.

In a separate mixing bowl or the bowl of a stand mixer, whip butter and sugars until light and fluffy. Whip in egg and vanilla extract and mix until well combined.

Gradually add flour/cocoa mixture to butter mixture, and continue mixing until well combined.

Use your hands to form the dough into a ball. Wrap in clingfilm/plastic wrap and chill in the refrigerator, at least two hours or overnight. While dough chills, prepare the homemade caramel.

Homemade Caramel:

Line a loaf pan with parchment, and grease generously with butter or nonstick cooking spray.

In a small saucepan, combine the cream, butter, and salt, and gently warm over low heat. (Do not boil.)

Meanwhile, in a large saucepan combine granulated sugar, water, and corn syrup and cook to medium caramel color (about 365° F / 185° C on a candy thermometer).

Remove caramel from heat. Pour in the warmed cream and butter mixture, then wait for a moment until the bubbles subside.

Return caramel pan to heat and cook mixture until it reaches approximately 250° F / 120° C on a candy thermometer.

Immediately pour hot caramel mixture into prepared pan and allow to set until firm, at least one hour or overnight.

Assembly:

When your dough is well-chilled and caramel is set, your cookies are ready to bake.*

Preheat oven to 350° F / 175°C. Line a baking tray with parchment or a silicone baking mat.

Remove caramel slab from loaf tin and peel away the parchment. Cut caramel slab into 1-inch squares with a sharp, well-oiled knife. (You’ll have a few squares of caramel left over for snacking!)

With a cookie scoop, portion out the cookie dough. Use your hands to roll each portion into a ball. You should have approximately 12 balls total.

Using your thumb, make a deep impression in each ball of dough, then press a square of homemade caramel into the middle. Shape the dough around the caramel until the caramel square is completely hidden.**

Place balls of dough on prepared tray. (Be sure to allow a good amount of space in between, as these cookies will spread!) Flatten slightly with the palm of your hand, then press 4-5 caramel M&Ms into the top of each ball. If you enjoy a gooey cookie and don’t mind a bit of a mess, you can press a few bits of the leftover caramel into the tops of your dough balls as well.

Bake in preheated oven for 10 minutes.

For perfectly round cookies, immediately reshape each cookie using a round cutter.

Sit tray on a wire rack and allow cookies to cool completely on the tray.***

Store cookies at room temperature in an airtight container, separated by sheets of wax paper or parchment, for up to five days.