METHOD

1. Preheat oven to 180°C (350°F). To make the chocolate base, place the flour, cocoa, brown and caster sugars and butter in a large bowl and mix well to combine. Using the back of a spoon, press the mixture into the base of a lightly greased 20cm deep-sided and loose-bottomed fluted tart tin. Bake for 15 minutes or until cooked through but still soft to the touch. Set aside to cool slightly. 
2. Reduce oven temperature to 150°C (300°F). Place the cream cheese, ricotta, peanut butter and vanilla in an electric mixer and beat for 5–6 minutes or until smooth. Add the sugar and beat for a further 3–4 minutes or until well combined. Scrape down the sides of the bowl and add the eggs, one at a time, beating well after each addition. Add cream and beat until just combined. 
3. Pour the cheesecake mixture over the chocolate base and smooth the top with a palette knife. Place the tin on a baking tray and bake for 45–50 minutes or until just set. Allow to cool in the fridge for 2 hours or until firm. Increase oven temperature to 200°C (400°F). To make the peanut praline, sprinkle the Demerara sugar in a thin and even layer on a large baking tray lined with non-stick baking paper. Bake for 20–25 minutes or until the sugar is melted and is dark-golden. Remove from the oven and quickly sprinkle with the peanuts. 
4. Allow to cool completely before breaking into pieces. Place the pieces in a small food processor and process until fine. To make the cream topping, place the sour cream, cream and caster sugar in a bowl and whisk until stiff peaks form. Top the cheesecake with the cream and sprinkle with the praline to serve. Serves 8–10.