Beat the butter, muscovado sugar, caster sugar and 2 tsp cinnamon together with an electric whisk for 2-3 mins until well-combined. Add the egg, flour, baking powder and raisins, if using, and continue to beat until the mixture becomes a uniform dough. Roll tablespoons of the dough into balls between the palms your hands (you should have 12-15). Chill in the fridge for at least 2 hrs until firm, or overnight. The unbaked dough balls will keep in an airtight container in the freezer for up to three months (see tip, below).

Heat the oven to 180C/160C fan/ gas 4 and line two large baking trays with baking parchment. Place the dough balls 3-4cm apart on the prepared baking trays to allow the mixture to spread without touching. Bake for 10-12 mins until lightly golden at the edges but still soft and gooey in the centre. Leave to cool completely on the baking trays.

Mix the icing sugar with the remaining cinnamon, then dust over the cookies. Will keep in an airtight container for up to five days.