Preheat the oven to 350°F (175°C). Grease an 8-inch square baking dish and set aside.

Put the chopped dates and water in a small pot. Bring to a gentle simmer for about 5 minutes, just until the dates soften. Remove from heat and mash the dates into a rough purée with a fork or potato masher. Let cool slightly.

In a mixing bowl, beat the softened butter with 3/4 cup dark brown sugar until light and fluffy. Add the eggs one at a time, beating after each until incorporated.

Whisk together the flour and baking powder. Fold the dry mix into the butter-egg mixture gently until just combined. Fold in the mashed date purée until evenly distributed.

Pour the batter into the prepared dish and smooth the top. Bake for about 35 minutes. The pudding is ready when the top is golden and a toothpick inserted into the center comes out with a few moist crumbs.

While the pudding bakes, make the toffee sauce. In a small saucepan over low heat, combine the heavy cream, remaining 1/4 cup dark brown sugar, butter, and vanilla. Stir until the sugar and butter melt and the mixture bubbles gently. Remove from heat and keep warm.

When the pudding is done, let it rest for a few minutes. Cut into squares and spoon warm toffee sauce over each serving. Serve immediately while warm.