METHOD

1. Line a 20cm round deep-sided loose-based cake tin with non-stick baking paper. Preheat oven to 160°C (325°C). Place the butter, caster sugar and vanilla in the bowl of an electric mixer and beat for 8–10 minutes or until pale and creamy. Scrape down the sides of the bowl and add the eggs, 1 at a time, beating well after each addition. Add the flour and beat on low speed until just combined. Spoon the mixture into the tin and bake for 30–35 minutes or until cooked when tested with a skewer. Allow to cool in the tin for 5 minutes before placing on a wire rack to cool completely. 
   
2. Use a skewer to make multiple holes in the cooled cake and place on top of the frozen base. Place the condensed milk, milk and buttermilk in a medium bowl and whisk to combine. Place the tin on a tray to catch any spills and pour the milk mixture, 1⁄2 cup (125ml) at a time, over the cake. Freeze for 30 minutes or until chilled.
3. Place the ice-cream in the bowl of an electric mixer and beat on low speed for 1–2 minutes or until softened. Spoon on top of the chilled cake and spread evenly. Freeze for 3–4 hours or until frozen. 
4. Place the cream, sour cream and icing sugar in the bowl of an electric mixer and whisk until stiff peaks form. Turn the cake out onto a cake stand or plate. Top with the cream and passionfruit and serve immediately. Serves 8–10