Preheat your oven to 160°C (320°F). Grease a 24cm (9-inch) round springform pan and line the bottom with parchment paper.

In a food processor, grind the almonds and pistachios until they are fine but still have a little texture. Mix the ground nuts with the powdered sugar and cardamom in a bowl.

In a separate clean, dry bowl, whisk the egg whites until stiff peaks form.

Gently fold the nut and sugar mixture into the egg whites using a spatula, being careful not to knock out too much air.

Pour the batter into the prepared pan and smooth the top. Bake for 35 to 40 minutes until the base is firm to the touch. Allow it to cool completely in the pan.

For the cream, combine the egg yolks, heavy cream, granulated sugar, and vanilla extract in a small saucepan.

Cook over medium-low heat, stirring constantly, until the mixture thickens enough to coat the back of a spoon. Do not let it boil. Remove from heat and let it cool to room temperature.

Once the custard base is cool, whisk in the soft butter a few cubes at a time until the cream is smooth, yellow, and fluffy.

Remove the cooled cake base from the pan and place it on a serving plate. Spread the yellow cream evenly over the top.

Refrigerate for at least 1 hour to set the cream before serving. Garnish with extra chopped pistachios if desired.