Tear open a large sitaphal in half using your hands.
Scoop out the pulp using a spoon into a chopper or a food processor.
Pulse 3-4 times.
The seeds will separate from the pulp.
Now remove them using a spoon and you have your sitaphal pulp ready to be used.
Heat whole (full-fat) milk in a heavy-bottom non-stick pan over medium heat.
Cook until the milk is reduced to half. Keep stirring frequently to avoid the milk from scorching.
Once the milk is reduced to half, add sugar and ground cardamom and stir well. Cook for another 3-4 minutes.
Remove the pan from heat and cover it with a lid to prevent the formation of a cream (malai) layer.
Let the basundi cool down completely. Once the basundi is cooled, add custard apple pulp to it and mix well.
Chill it for a few hours. Garnish with slivered nuts and dried rose petals and serve chilled.