Preheat the oven to 180C / 350F / 160C fan forced, and line 2-3 large cookie sheets with baking paper.
Sift the flour and cocoa into a bowl and set aside
Beat the butter and sugar together until lightened. Scrape down the sides of the bowl. Add the egg and beat well, scraping down the bowl a couple of times until well mixed.
Add the flour mix in 3 parts, keeping the mixer on low until it comes together as a dough.
Bring the dough into a smooth ball and roll out between 2 sheets of baking paper (I cut the dough in half as I find it more manageable to do half at a time). Roll it to about 4-5mm thick. The thinner you go, the crispier they will be when finished cooking. The thicker you roll it, the softer the finished cookie will be. I like them 4-5mm as this creates a nice crispy edge and soft centre. Use your cookie cutter of choice to cut out cookies. Reroll the dough as required but get as many out of each rolled batch of dough as possible.
Bake for 5 minutes, turn the baking trays and bake for another 5 minutes.
For the Peppermint fondant
Beat all ingredients together until thick but smooth and creamy
Line a large baking tray with plastic wrap then tip the peppermint mixture out on top. Lay another sheet of plastic wrap over the top and use your hands to press it out to about 4-5mm thick.
Place the tray in the freezer for one hour.
Use the same cookie cutter you used for the cookies to cut the peppermint fondant and use a flat metal spatula to help you transfer them onto the cookies (notes)
If there is scraps of peppermint fondant, you can flatten it out and freeze again, to finish any remaining cookies.
Place the peppermint topped cookies in the freezer for half an hour.
Melt the chocolate in 30 second increments in the microwave, stirring well between each. When there are just a few lumps left, set it aside for a few minutes before giving it a final stir.
Line a baking tray with baking paper and sit a wire rack over the top. Use two forks to place a cookie into the melted chocolate and turn it over to cover in chocolate. Lift the cookie out of the chocolate and allow excess chocolate to drip off, then give it a gentle shake to smooth out the top. Place the cookies on the rack for about 5 minutes before transferring to a plate to set in the fridge.
I use a standard Australian 20ml tablespoon (4 teaspoons worldwide)
The peppermint fondant will be very soft and room temperature so work quickly and refreeze if you need to, to make topping the cookies easier.
For best results you should always weigh ingredients like flour and sugar. Kitchen scales are relatively cheap but if you can’t weigh the ingredients, use the spoon and level method (don’t scoop).