Place the chopped dates in a heatproof bowl with baking soda and pour over boiling water. Let sit for 10 minutes, then mash into a chunky paste with a fork or spoon.
In a large bowl, beat together softened butter and dark brown sugar until the mixture is pale and fluffy, and you can hear a faint creaming sound.
Add eggs one at a time, mixing well after each to incorporate fully. Stir in vanilla extract for added depth of flavor.
Gently fold in the sifted flour, mixing just until combined to keep the batter tender and airy.
Stir in the mashed date mixture until evenly incorporated. The batter will be thick and sticky.
Pour the batter into a greased baking dish and smooth the top with a spatula. Bake at 180°C (350°F) for 30–35 minutes, or until the top is golden and a toothpick inserted comes out moist with crumbs.
While the pudding bakes, prepare the toffee sauce: combine brown sugar, heavy cream, and butter in a saucepan. Bring to a gentle simmer over medium heat, stirring until the mixture thickens slightly and becomes velvety.
Remove the pudding from the oven and poke holes all over the top with a skewer or fork. Pour the warm toffee sauce evenly over the hot pudding, allowing it to soak in and become sticky.
Let the pudding rest for about 5 minutes to absorb the sauce. Serve warm, with extra toffee sauce drizzled over and a scoop of vanilla ice cream or whipped cream if desired.
