No need to preheat the oven yet, this dough needs to chill!
Place flour, cocoa powder, cornflour, bicarb, salt and chocolate chips into a medium sized bowl and mix until all the chocolate chips are coated in flour. Leave to one side.
Place butter and sugar into a large bowl, or the bowl of your stand mixer and beat on medium-high speed until light and fluffy, around 2 minutes.
Add in the eggs and peppermint extract, scraping down the sides of the bowl as necessary and mix on med-high speed until well combined and smooth, around 1 minute.
Add in the 1tbsp of brewed coffee and tip in the flour/cocoa mixture. Mix on low until a soft dough forms and there are no lumps of flour.
Transfer the dough to a medium sized bowl (the one you measured the flour in is fine) and cover with cling film. Place in the fridge to chill for at least 6 hours, overnight if possible.
Once the dough is chilled, preheat the oven to 180C/350F and line 2-3 baking trays with a silicone mat/Silpat/grease proof paper.
Using a 1.5tbsp cookie scoop, place dough balls 2 inches apart on the baking trays and flatten them ever so slightly with the palm of your hand, so they don’t roll away!
Place in the oven for 9-11 minutes, until the edges are slightly crisp, but the middle still looks a little soft. If you look in the light of the oven, the top will look kind of matte and not wet and shiny.
Leave to cool on the baking trays.
At this stage, you can stop and enjoy the Peppermint Mocha Cookies or you can place the melted white chocolate into a small bowl and dunk each cookie into the chocolate, to cover each cookie half way.
Place on a wire rack with kitchen paper underneath it and sprinkle with Christmas sprinkles. Leave for 45 minutes – 1 hour to set before enjoying!
Peppermint Mocha Cookies will keep in an airtight container, at room temperature for 5 days.