Grease an 8-cup-capacity pudding bowl or a decorative bundt pan very well with soft butter. If you're using a pudding bowl, line the base with baking paper.
2 Tbsp butter
Put the flour, baking powder, baking soda, spices, sugar and chopped ginger in a bowl and whisk to combine.
2 cups all-purpose flour, 2 tsp baking powder, 1/2 tsp baking soda, 1 Tbsp ground ginger, 1 tsp cinnamon, 1/4 tsp ground nutmeg, 1/4 tsp ground cloves, 1/4 tsp ground white pepper, 2/3 cup dark brown sugar, 2 Tbsp chopped stem ginger
Put the eggs, milk, treacle and melted butter into another bowl and whisk to combine, then pour this mixture over the flour and stir well until smooth. Pour mixture into prepared pudding bowl and smooth the top.
3 eggs, 1/2 cup milk, 1/4 cup treacle, 6.5 oz unsalted butter
Place a sheet of parchment paper on top of a sheet of foil; it should be big enough to easily fit over the top of the pudding bowl with a good amount of overhang on two sides. Fold the paper and foil to shorten the overhanging sides and make a pleat in the centre. Place, foil-side up, over top of pudding and scrunch foil and paper around edge of pudding bowl.
Put the pudding into your steam oven and set to steam, 212°F/100°C (100% humidity) for 2 1/2 hours.
While the pudding cooks, make the butterscotch sauce. Place butter, sugar, cream and salt in a saucepan over medium heat and cook, stirring occasionally, until melted and combined. Bring to a simmer, then continue to cook, stirring occasionally, for 5 minutes or until sauce thickens slightly. Remove from heat and keep warm (or let it cool and reheat later; see notes).
3.5 oz unsalted butter, 1 1/2 cups dark brown sugar, 1 1/2 cups heavy cream, 1/2 tsp fine salt
When the pudding is done, remove it from the oven and let it sit for 5 minutes. Discard foil and baking paper and turn onto a serving plate or shallow bowl (you need something with sides, so the sauce doesn't run off!). Dollop with whipped cream and drizzle with about half of the warm butterscotch sauce. Serve immediately in wedges, with remaining sauce on the side.
whipped cream