Crush the Tennis biscuits and mix with melted butter. Press into the base of the springform pan.
Beat cream cheese until smooth. Gradually add condensed milk and vanilla, mixing well.
Add eggs one at a time, mixing gently after each addition.
Pour the cheesecake filling over the biscuit base.
Bake at 160°C (320°F) for 45-50 minutes, or until set.
While the cheesecake bakes, prepare the malva sauce: Combine cream, butter, brown sugar, vinegar, and apricot jam in a saucepan. Simmer over low heat until thickened.
Let the cheesecake cool completely before pouring the malva sauce over the top.
Refrigerate for at least 4 hours before serving.
Notes
For a richer flavor, use full-fat cream cheese and cream.