Cream butter, sugar and vanilla with paddle attachment.
Add egg and water. Mix until light in color and fluffy
In a separate bowl, sift together flour, baking powder and salt.
Mix dry mixture into creamed mixture, then add in the chocolate chips and mix until just incorporated.
Test if dough will come togetherby squeezing it together to form a ball. If it falls apart, add another 1 tsp of water.
Divide dough into 2 balls. Cover with plastic wrap and pop into the freezer for 5 mins.
On a lightly floured work surface, roll out the dough to ¼ inch thick. Cut witha cookie cutter (I like scalloped edges). Place on a silicone baking mat or parchment lined baking sheet.
Bake at 375 degrees F for 8 –10 minutes (9 mins is the sweet spot in my oven). The cookies will be soft to touch but will firm up as they cool down.
Allow to cool completely before frosting.
For the Frosting
Combine the butter, confectioner’s sugar, cocoa powder, heavy cream, vanilla and pinch of salt in the bowl of stand mixer with the whisk attachment (or use an electric handheld mixer).
Starting on low speed, beat the ingredients together until the start to combine, then increase the speed to medium-high and beat until creamy and fluffy.
Using a butter knife or palette knife, spread the frosting on the cookies. If desired, put the cookies in the fridge for 15 minutes to allow to frosting to harden.
Store in an airtight container at room temperature for up to a week, or in the fridge for up to 2 weeks.