Preheat the oven the 375 degrees Fahrenheit. Line a cupcake pan with cupcake lines and set it aside. In a medium-sized bowl, mix together the flour, baking powder, and salt until combined. Set aside.

In the bowl of an electric stand mixer fitted with the paddle attachment, cream together the butter and sugar until smooth and fluffy. Add the eggs, one at a time, waiting until each is incorporated before adding the next one. Mixing at low speed, alternate between adding the milk and the flour mixture in three rotations until they're all incorporated into the batter. Add the vanilla extract and rose water and stir to combine.

Fill the cupcake liners 3/4 full of the batter and place the pan in the oven. Bake until the edges are very faintly golden and a toothpick inserted into the center of the cupcake comes out clean, about 15 minutes. Remove from the oven and allow to cool for 10 minutes before removing the cupcakes from the pan and placing them on a wire rack to cool completely. Place the remaining cupcake liners on the cupcake pan and fill with the remaining batter and repeat the baking cycle.

Place all of the ingredients in a blender or food processor and blend until relatively smooth. Set aside.

In the bowl of an electric mixer fitted with the paddle attachment, beat the butter at medium high speed until pale and fluffy, about 4 minutes. Reduce the speed, add the powdered sugar, and once it's incorporated, raise the speed back to medium high and beat until fluffy, about 3 to 5 minutes. Reduce the speed to medium, add the milk, one tablespoon at a time, and then the vanilla extract. Set aside.

Once the cupcakes have cooled. use a small spoon to scoop about 1 tablespoon of cake out of the top center of each cupcake. Fill the hole with the pistachio cream until level. Spread the buttercream on top of the cupcakes, taking care not to press down too hard on the area with the filling otherwise it will squirt out the side and get messy.

Spread the chopped pistachios in a low pile on a clean working surface, like a cutting board. Roll the *very* edges of the frosted cupcake in the chopped pistachios to get the nut bits to adhere to the buttercream around the edges of each cupcake. Repeat with all of the remaining cupcakes. Garnish the top center of each cupcake with a shelled pistachio and serve.