Beat 1 tbsp butter and 1 tbsp grated jaggery together and spread over base and sides of a 7" cake tin.
Top with pineapple slices and walnut halves.
For the cake:
Melt the butter, honey and jaggery.
Cool and whip in yoghurt, milk and egg.
Stir in dry ingredients. Pour over base in tin.
Bake in a preheated oven at 170 degrees C for 30 minutes.
Remove from oven and turn out.
Serve warm with prepared custard, to which 3 tbsp thick yoghurt and 3 tbsp whipped cream has been beaten in.