Line a baking tray with baking paper and set aside (one with no lip is best).
Add the all purpose flour and cold, cubes of butter to a large mixing bowl. Use your finger tips to rub the flour into the butter. You can use a curved dough scraper if you prefer.
Once the butter is fully coated in flour, add the baking powder, salt, brown and white sugars and chocolate chips to the bowl. Gently combine all of the dry ingredients so that they are well mixed through and the chocolate chips are well distributed.
In a small mixing jug, combine the egg, sourdough starter, heavy whipping cream and vanilla. Whisk together until well combined.
Now pour the liquid ingredients into the dry ingredients. Use a wooden spoon or rubber spatula to bring the mixture together to a very shaggy, dry dough. It's ok if it's lumpy and has spots of flour through it - the main thing here is not to overwork the dough!
Grab your baking tray lined with parchment paper and tip the shaggy dough out onto it. Use your hands to gently press the dough into a round disk (mine is around 11" or 30 cm across).
Use your dough scraper or a sharp knife to cut the disc into quarters and then each quarter in half, so you end up with 8 equal wedges. Gently move them apart, so they have room to bake.
Place the baking tray in the fridge (it should stay there for around 30 minutes to make sure the butter is super cold). Preheat the oven to 400F/200C. After 30 minutes, remove the dough from the fridge and gently brush the scones with the heavy whipping cream (pastry brush is best for this). Sprinkle with sugar if you want to.
Place the scones into a 400F/200C oven for around 15 to 20 minutes - or until the scones are golden brown.
When they're cooked, remove the tray from oven and allow the scones to cool on the tray for around 10 minutes before you enjoy them!