Preheat the oven to 200°C.
Place chopped pumpkin on a tray, dot with 25g butter, sprinkle with sugar, drizzle with syrup, and bake for 30–35 minutes.
Crush the gingernut biscuits into fine crumbs using a food processor or rolling pin.
Stir 50g melted butter into the biscuit crumbs until combined.
Press the biscuit mixture into the bottom of four rings on a lined baking tray to form bases.
Purée the roasted pumpkin and its juices in a food processor until smooth.
Mix whipped cream, cream cheese, yoghurt, and chopped stem ginger in a bowl.
Swirl the pumpkin purée into the cream mixture and spoon onto the biscuit bases.
Smooth the tops and chill in the fridge for 1–2 hours until set.
Remove from rings and garnish with extra stem ginger before serving.