In a bowl, whisk together butter, sugar, salt and vanilla until foamy. Then add one egg and combine it well with the dough before adding the second one.
In another bowl, mix baking powder and flour. Add flour to the mixture in three parts, alternating with milk, whisking well after each addition.
Once the mixture is smooth and homogeneous, incorporate the grounded pistachio nuts into it with a spatula.
Place a cupcake liner into each slot on the cupcake pan and fill them up to 3/4 of their capacity.
Bake the cupcakes at 180°C for 25-30 minutes, then let cool completely.
Meanwhile, whip the cream until stiff in one bowl and in another, mix mascarpone and pistachio cream. Gently fold the cream under this mascarpone cream. Add sugar if necessary. Then cover it with plastic foil and place in the refrigerator until solid.
Once the cupcakes have cooled, fill a piping bag with a star-shaped nozzle with mascarpone cream and decorate.
Finally, decorate with some grounded pistachios and a few drops of pistachio cream.