In a large mixing bowl, combine the sugar and butter until fluffy.
Add the eggs, milk, vanilla and lemon extracts and mix until smooth.
In a medium bowl, combine flours, baking power and salt.
Add the dry ingredients to the wet in batches stirring well.
Drop soup spoonfuls (or medium-sized ice cream/cookie scoop) of dough 2 inches apart on butter baking sheets.
Bake at 375 degrees until edges begin to brown, 20 to 30 minutes.
Let cool completely.
To make frosting, put confectioners' sugar in a bowl. Stir in enough water to make the mixture thick and spreadable. Remove half the frosting to another bowl. Add melted chocolate and still till smooth. Frost half the cookies with chocolate frosting and the other half with white frosting.
Notes
If you don't have or can't find cake flour, you can make it yourself. Check out Sally's Baking Addiction.