Method

​1 Preheat the oven to 190°C/fan 170°C/gas mark 5 and line two baking trays with baking parchment paper.

2 Beat the butter and sugar (with an electric whisk) in a bowl until light and fluffy. Beat in the egg yolk and vanilla extract.

3 Next add the gluten-free flour, cocoa powder, chocolate chunks and stir until well combined.

4 Scoop up a generous spoon of the mixture and place on to the baking tray and then flatten it to look like a cookie shape. They will spread out when they bake so I recommend only having six cookies to a tray.

5 Bake in the oven for 12–15 minutes. They are soft when they first come out of the oven but they harden as they cool. Leave on the baking trays for 5–10 minutes to cool and then transfer to a wire rack.