Preheat oven to 350 degrees.
In a large bowl, cream together butter and sugar for 3 minutes. Add eggs, one at a time beating well after each addition. Beat in vanilla. Add baking powder, salt and one cup of flour and beat until incorporated. Add the rest of the flour, one cup at a time beating after each addition until incorporated. Set aside.
In a medium bowl, mix all filling ingredients until well combined.
Spread half the batter in a greased 15x10 baking pan. Spread filling evenly over batter. Drop the remaining batter by the spoonful over the top and spread out.
Bake for 40-45 minutes or until golden brown. Meanwhile, make the glaze. In a small bowl, combine all glaze ingredients until smooth. After cookies are cooled, pipe on the glaze. Enjoy!