In a bowl, whisk together the flour, sugar, baking soda and cream of tartar.
Using your fingertips, crumble the butter into the flour mixture.
Add the lemon zest, crushed Walkers Shortbread crumbs and the chocolate chips.
In another bowl combine the cream, vanilla and lemon juice.
Pour into the flour and stir well with your hands until the mixture forms a sticky ball.
Dump the dough out onto a well floured work surface and form into a flat rectangle about an inch thick.
Using a sharp knife dive the dough into equal sized triangles and place on the prepared baking tray close to one another.
Brush the scones with the milk and sprinkle with the remaining crushed cookie crumbs.
Bake in the oven for about 25-30 minutes or until the scones feel firm when pressing your finger on top of them.
Whisk the powdered sugar with the lemon juice and drizzle over the scones once they have cooled.