For about 16 cupcakes:
1 cup shelled pistachios
140gr unsalted butter, at room temperature
90gr mascarpone, at room temperature
1½ cups caster sugar
3 large eggs
1 tsp. vanilla extract
1½ cups cake flour (not the self-rising type), sifted
1½ tsp. salt
For the ganache:
140gr Valrhona 68% chocolate (or your favourite dark chocolate), finely chopped
30gr unsalted butter, at room temperature
Additional chopped pistachios, for garnish
First, prepare the pistachios. Note that it does not really matter whether they are salted or unsalted, as by the time you are done processing them the salt will have been washed off. Rub the pistachios between your palms to remove as much of the dry skin as possible, then rinse them a couple of times in cold water and leave them to soak for about 10mn, before removing the rest of the skin (which by now will have softened and should come off easily).
Pat the pistachios dry with a kitchen towel, reserve a few of the greener ones and grind the others to a fine powder using a food processor or a mortar and pestle.
Preheat the oven to 180˚C and line cupcake pans with paper liners.
In a bowl, combine the butter and mascarpone and beat with an electric mixer medium-high speed until light and fluffy.
Add the ground pistachios.
Gradually mix in the sugar on medium-low speed, scraping down the sides of the bowl as needed.
Beat in the eggs one at a time, mixing well after each addition. Add the vanilla extract.
With the mixer on low speed, add the flour and salt, and mix just until the dry ingredients are incorporated.
Fill each paper cup about three quarters full and bake for 20 to 25mn.
Let cool in the pan a few minutes, then transfer to a wire rack to cool completely.
To make the ganache, place the chopped chocolate in a small heatproof bowl.
Bring the mascarpone to a simmer in a small saucepan over medium-high heat.
Pour the warm mascarpone over the chocolate and let stand 1-2 minutes.
Whisk in small circular motions until the chocolate is completely melted and the ganache is smooth and glossy.
Whisk in the butter until completely incorporated.
Cover the top of each cooled cupcake with the ganache to create an even layer (let the ganache cool and thicken a bit beforehand).
Sprinkle with the remaining chopped pistachios. Do not refrigerate the cupcakes as this would cause the ganache to lose its glossy aspect.
Pop any leftover ganache into a piping bag and practise your piping skills! You can freeze the results for a couple of months and they make fabulous toppings for ice cream (or more cupcakes!).