Melt all of the ingredients together in a saucepan over medium heat. With a rubber spatula, constantly stir the mixture together as it melts together. Once all of it has melted and combined, transfer it to a medium sized casserole dish, so it can cool down faster, and cover it with plastic wrap that touches the surface of the frosting.

Let it cool down to room temperature in the fridge for 1-2 hours. Give it a gentle stir at 1 hour to make sure it cools down evenly.

Preheat the oven at 170ºC conventional oven and prepare 2 x20 cm baking pan with parchment paper.

Start by blending the pistachios into a flour-like consistency.

Sift together the blended pistachios, all-purpose flour, baking powder, baking soda and salt and set it aside.

In a large bowl using an electric hand mixer or in a bowl of a stand mixer, add the butter, and granulated sugar and mix it on high speed for 3 minutes.

Add the eggs two at a time into the mixture and mix it in until combined.

Continue by adding half the dry ingredients, on low speed, mixing until just combined.

Then add the sour cream, vegetable oil, vanilla extract and mix until just combined. Then add the other half of the dry ingredients and mix until combined.

Using a rubber spatula, give the batter a gentle fold to make sure all of the ingredients have combined.

Pour the cake batter into the prepared pans and bake for 30-33 minutes or until a cake tester comes out clean.

Let the cakes cool on a cooling rack. After 10 minutes, gently remove the cake from the cake tin and let the cakes cool down completely.

Place the first cake layer on your serving dish or your turntable. Add 2 big scoops of frosting and with an offset spatula, even it out and place it in the fridge for 10 minutes.

Add the other cake layer on top and cover the whole cake in the remaining frosting. To finish with decorate with chopped pistachios.