Preheat oven to 400 and line 2 baking sheets with parchment paper and set aside.
Add butter, baking powder, vanilla and salt to a mixing bowl and beat until combined.
Beat in sugar, followed by egg, making sure mixture is combined well.
Add the flour to the butter mixture alternating with the milk. Do not over beat, just beat until combined.
Using a tablespoon portion scoop, drop batter onto prepared baking sheets. Spray your fingers with nonstick cooking spray and gently press batter into a 1-1/2" circle.
Bake for 8-10 minutes or just until browned on the bottom. Remove from oven and let stand to cool completely before icing.
Add chocolate chips, corn syrup, vanilla and heavy whipping cream to a saucepan.
Heat over medium heat, stirring frequently until nearly smooth and melted. Make sure the mixture doesn't bubble and boil. Remove from heat and continue to stir until smooth and all chocolate chips are melted.
Add powdered sugar and use a hand mixer to beat until smooth. Let stand to cool slightly.
To ice cookies, dredge the bottom of each cookie into the chocolate icing and place, icing side up, onto parchment paper. Repeat until all cookies are iced.
Let stand to harden, or pop in the fridge for 15 minutes to harden.
Repeat and dredge cookies in icing for a second time.