Preheat your oven to 350°F (175°C) and generously grease an 8x8-inch baking dish with butter. In a medium heatproof bowl, combine the chopped dates, boiling water, and baking soda.

Let the date mixture sit for 15 minutes to soften, then mash it lightly with a fork until it resembles a chunky paste. Set aside to cool slightly.

In a large mixing bowl, beat the softened butter and dark brown sugar together until light and fluffy, about 2 minutes. Add the eggs one at a time, beating well after each addition.

Gently fold the flour and baking powder into the butter mixture until just combined. Stir in the mashed date mixture, including any unabsorbed liquid, until a uniform batter forms.

Pour the batter into the prepared baking dish and smooth the top. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean and the sponge is springy to the touch.

While the pudding bakes, make the toffee sauce. In a medium saucepan, combine the butter, heavy cream, dark brown sugar, vanilla extract, and sea salt over medium heat.

Bring the sauce to a gentle boil, stirring frequently. Reduce the heat and simmer for 5 minutes until it thickens slightly, darkens in color, and coats the back of a spoon.

Once the pudding comes out of the oven, use a skewer or fork to poke holes all over the warm sponge. Pour half of the warm toffee sauce evenly over the top, letting it soak in for at least 10 minutes.

Slice the soaked sponge into squares and serve warm, pouring the remaining hot toffee sauce over individual portions. Pair with a scoop of vanilla ice cream or a dollop of whipped cream for the perfect finish.