Add flour, rolled oats, coconut, caster sugar and salt to a large mixing bowl. Stir through until well combined.
In a small saucepan, melt the butter gently. Once melted, stir through the golden syrup until mixed through.
Add the bicarbonate soda to the butter & golden syrup and stir (it should foam a little).
Now, add the sourdough starter and melted butter mixture to the bowl of dry ingredients.
Stir through until it forms a biscuit dough.
Using a spoon, scoop the mixture and form into balls. 30g is a good size for each ball.
Place the balls of dough onto a baking tray lined with parchment paper. Make sure there's plenty of room between them as they will spread out.
Flatten the balls out a little with the back of a wet spoon.
Bake them in an oven at 180C for around 12 - 15 minutes. They will still be soft when you take them out but will harden up once they're cooled.