In a stand mixer bowl, combine the flour, sugar and baking powder. Add the butter and mix until you get crumbs.
Add the egg, egg yolk and heavy whipping cream and process into a soft and smooth dough. Wrap in plastic wrap / parchment paper and refrigerate for about an hour.
Mix the filling ingredients in a bowl and set aside.
Dust your working surface with flour and roll out the dough until it is about ½" an thick.
Preheat the oven to 340 °F (170 °C).
Cut out 3" circles using a cookie cutter. Add the filling to a piping bag and squeeze a little right in the center of each circle.
Sprinkle some pistachio pieces on top, close the dough as shown in the video, tighten the edges and leave a very small opening (the dough will expand while baking so it is important to tighten well).
Line a sheet pan with parchment paper and bake for 12-15 minutes, or until the cookies turn golden.
Remove from the oven and let the cookies cool off for 10 minutes.
Sprinkle with powdered sugar and drizzle some leftover filling on top.