Begin by grinding the shelled pistachios in a food processor until they reach a fine meal texture—be careful not to over-process into a paste. In a mixing bowl, combine the ground pistachios with all-purpose flour, baking powder, and salt.

In a large mixing bowl, beat together the softened unsalted butter and granulated sugar until the mixture is light and fluffy, about 3-5 minutes. Add the eggs one at a time, mixing well after each addition. Stir in the milk, vegetable oil, and both vanilla and almond extracts, ensuring everything is well combined.

Preheat your oven to 175°C (350°F) and prepare three greased 8-inch round cake pans. Divide the prepared cake batter evenly between the pans, smoothing the tops. Bake for 22-25 minutes, or until a toothpick inserted into the center comes out clean. Once baked, allow the layers to cool in the pans for about 10 minutes before transferring them onto a wire rack to cool completely.

While the cake layers cool, it's time to whip up the mascarpone cream. In a chilled mixing bowl, whip the heavy cream until soft peaks form. Gently fold in the mascarpone cheese and powdered sugar, mixing until the cream is smooth yet still fluffy.

Once your cake layers are completely cool, it’s time to assemble the masterpiece. Place the first layer on a serving plate and spread a generous layer of the mascarpone cream on top. Repeat this with the second layer. Finally, use the remaining mascarpone cream to frost the top and sides of the cake.

To allow the flavors to meld beautifully, refrigerate your assembled Pistachio Mascarpone Layer Cake for at least 2 hours before serving.