Chocolate Shortbread Twirls

250g butter, melted; 1 cup sugar; 1 egg; 1 tsp vanilla essence; 2 cups flour; mix dough and divide into 2 bowls; add a quarter cup of drinking chocolate powder to one, and a quarter cup of flour to the other; knead. I added a handful of choc chips to the dark dough and a half handful of chocolate hail to the light dough. Lay out, roll and chill, then slice and bake at 200°C for about 10 minutes, watching carefully. Have fun!
Note: In the video, I made a double quantity of this recipe.