Pistachio Cake with Buttercream

For the Cake

• •100 g ground pistachios (Aegina pistachios)
• •240 g whole milk
• •1 tablespoon (15ml) white vinegar
• •300 g '00' flour
• •1 teaspoon (6 g) baking powder
• •¼ teaspoon (1 ½ g) baking soda
• •1/4 teaspoon salt
• •60 g unsalted butter, at room temperature
• •200 g sugar
• •4 eggs (M)
• •60 g sunflower oil or other light oil
• •1 teaspoon (5g) vanilla extract
• •40 g rosewater

For the Pistachio Ganache

• •300g white chocolate
• •120g pistachio paste
• •160g heavy cream
• •380g chilled heavy cream

For the Buttercream

• •750g powdered sugar
• •375g softened unsalted butter
• •10g milk or heavy cream
• •5 g vanilla extract

For the Syrup

• •250ml water
• •250g sugar
• •10 g rosewater

For Decoration

• •ground pistachios
• •dried roses

Prepare the pistachio ganache the day before:

1. 1. Chop the chocolate into small pieces and place it in a bowl. In a small saucepan, bring 180g of heavy cream to a good boil and pour it over the chopped chocolate. Stir until the chocolate melts. If it doesn't melt completely, return the mixture to the heat and whisk until the chocolate is fully melted.
2. 2. Next, add the chilled heavy cream and whisk. Transfer the ganache to a glass bowl, cover with plastic wrap (to prevent the surface from hardening), and refrigerate overnight. Preheat the oven to 180°C (fan-assisted). Grease the sides of a 20cm baking pan and line the base with parchment paper.
3. 3. In a small bowl, mix the milk with the vinegar and let it sit for 5-10 minutes to 'curdle' (this creates buttermilk). In another bowl, sift the flour, baking powder, and baking soda, then add the salt. In the bowl of a stand mixer, beat the butter with the sugar for 10 minutes until light and fluffy. Add the eggs one by one, beating well after each addition. Scrape down the mixture with a spatula and add the oil, vanilla extract, and rosewater.
4. 4. Reduce the mixer speed and alternately add the flour mixture and the milk mixture in 2 batches, starting and ending with the flour. Gently mix with a spatula or on low speed in the mixer. Finally, add the ground pistachios and mix until evenly combined.
5. 5. Pour the mixture into the pan, smooth the surface, and bake in the preheated oven for 35-40 minutes, or until a knife inserted into the center comes out clean. Let cool in the pan for 10 minutes, then unmold and let cool completely on a wire rack.

For the Buttercream:

1. 1. The powdered sugar plays an important role in the buttercream. If you can't find very fine powdered sugar, you should grind it well and sift it 2-3 times.