Whisk together cream, eggs and vanilla. set aside,
In large bowl whisk together flour, sugar, baking powder, salt and lemon zest. Using pastry blender or 2 knives cut in butter until you have coarse crumb mixture, stir in chocolate, with a fork stir in cream mixture until dough forms.
Turn out on lightly floured surface and roll out into a 9 inch square..cut this into 9 squares..half each square diagonally..place 1 inch apart on parchment lined baking sheet...whisk egg yolk with 1 tsp water and brush over scones ...Bake in 425F oven until golden about 13 to 15 minutes...serve warm can be reheated in toaster oven but they are still good not heated. great with a cup of coffee.