Heat 1/4 cup of the thick cream from the top of the coconut milk over high heat for 5 minutes, stirring often, until the cream bubbles. To separate, pour the milk into a jar and allow to sit for 2-3 hours or until you can see two distinct layers.
Add curry paste and cook for 2-3 minutes stirring constantly until well combined.
Add peanut butter, fish sauce and brown sugar and cook for 2-3 minutes, stirring constantly. Add remaining coconut milk.
When the mixture boils, add rump steak, cover and cook over medium heat for 5 minutes, stirring a few times.
Stir through basil leaves.
Serve with steamed jasmine rice and top with extra basil leaves and shredded red chilie and lime leaf, if desired.