Preheat the oven to 350°F / 180°C. Line two cookie sheets with baking parchment paper.
Cream the butter and both sugars in a mixing bowl with an electric mixer until light and fluffy, then beat in the mint extract.
In a separate bowl, whisk the flour, cocoa powder, baking soda and salt together.
Stir the milk and dry ingredients into the wet mixture by hand (don’t use the electric mixer or the dough will be tough).
Stir in the chocolate, then roll tablespoons of the dough into balls, place onto the baking tray (don’t crowd them as they’ll spread), and press them down slightly with the heel of your hand.
Bake for 10 minutes, then leave to cool on the tray for 2 minutes, then transfer to a wire rack to cool completely.
Crush the candy canes (I put them into a bag and crush with a rolling pin).
Melt the chocolate, then swirl onto the cooled cookies. Sprinkle with the crushed candy canes.
Storing: These cookies will stay fresh in an airtight container on the counter or in your pantry for up to 2 weeks.Freezing: You can freeze the cookie dough before it’s baked or even freeze the baked cookies. Just make sure each is sealed properly in a bag with as much air taken out as possible. Thaw overnight in the fridge for the dough and thaw on the counter for baked cookies.Dip half in white chocolate before sprinkling with crushed candy canes. Dust them with powdered sugar for a snowy look.Try adding extra chocolate chips, dark, milk, butterscotch...