In a food processor, pulse shelled pistachios until finely chopped but not pasty. In a mixing bowl, whisk together the chopped pistachios, all-purpose flour, baking powder, and salt until well combined.

Using a stand mixer or hand mixer, beat the softened unsalted butter and granulated sugar together on medium speed for about 3 minutes, or until light and fluffy.

Add the room temperature eggs one at a time, then add whole milk, vegetable oil, and vanilla extract, blending until smooth.

Gently fold the dry mixture into the wet ingredients using a spatula, mixing until just combined.

Preheat your oven to 175°C (350°F). Divide the batter among three greased and lined 8-inch round cake pans. Bake for 22-25 minutes.

Once baked, cool the cake layers for 10 minutes in the pans, then transfer to a wire rack to cool completely.

In a chilled bowl, whip heavy cream until soft peaks form. Add mascarpone cheese, powdered sugar, and vanilla extract, and whip on low until smooth.

Place the first cake layer on a serving plate, spread mascarpone cream on top, and repeat with the second layer. Frost the top and sides with the remaining cream.

Refrigerate the assembled cake for at least 2 hours before serving.