Preheat oven to 170 degrees Celsius and line a 23-24cm round springform cake tin with baking paper.
Place a small saucepan over low to medium heat and add the butter, Low GI Sugar and vanilla extract. Allow to melt, and stir to combine everything. Continue to stir until all the butter has melted and the sugar has mostly dissolved away.
Leave the butter mixture to cool a little, then transfer to a large mixing bowl. Whisk in the milk and the egg.
Then add the flour, and sift in the bicarb soda. Add the chocolate and nuts, mix to combine with a wooden spoon.
Tip the dough into the prepared tin and push the dough out so it reaches the edges and fits evenly in the tin.
Bake for 25-30 minutes or until golden brown.
Remove from the oven and place the cookie on a wire rack, leaving it in the cake tin until cooled and ready to remove.
Store in an airtight container, will keep for 5 days.