In a bowl, beat the butter and sugar until creamy. Add the eggs one at a time until incorporated.
In another bowl, mix the flour, salt, baking powder and cocoa powder. Add this to the butter mixture and mix well.
Add the red food coloring until you get the right rich red color. Then mix in the white chocolate on a low speed and roll the mixture in cling film. Leave to rest in the fridge for at least 2 hours.
Roll the dough into balls about the size of a two euro coin/dollar coin. Roll the balls in a bowl of icing sugar and place on a baking tray lined with parchment paper. You can roll them twice for an extra nice crinkle effect.
Bake for 12-14 minutes at 180°C/350˚F (conventional oven) until golden brown.
Tips
For the reddest cookie, reduce the amount of cocoa powder.