Preheat the oven to 160°C (fan). Line a baking sheet with parchment.

In a mixing bowl, cream together the butter and sugar until light and fluffy.

Beat in the egg until fully combined.

In a separate bowl, whisk together the flour, cocoa powder, bicarbonate of soda, salt, and chocolate pieces. Fold the dry ingredients into the butter mixture until a soft dough starts to form.

Stir in the yogurt, vanilla extract, and red food colouring, mixing until the dough is smooth and evenly coloured.

Shape the dough into even logs, wrap, and chill in the fridge for at least 1 hour to firm up.

Slice the chilled dough into rounds and arrange on the prepared baking sheet, leaving room for spreading.

Bake for 7–8 minutes, or until the edges are set but the centres remain slightly soft.

Allow the cookies to cool on the tray for a few minutes before transferring to a wire rack — or enjoy them warm for a richer, fudgier bite.