Place the chopped dates in a heatproof bowl. Pour the boiling water over the dates, stir in the baking soda, and let sit for 10 minutes so the mixture softens and becomes slightly thickened. Mash lightly with a fork to break up large pieces.

Preheat and prepare pan

Preheat the oven to 350°F (175°C). Lightly butter an 8-inch square or similar-size baking dish (about 2-quart capacity) and line the base with parchment if you prefer easier removal.

Cream butter and sugar

In a mixing bowl, beat the 1/2 cup softened butter with 3/4 cup brown sugar until pale and fluffy, about 2–3 minutes using a hand mixer or 4–5 minutes by hand.

Add eggs and vanilla

Beat in the eggs, one at a time, ensuring each is incorporated before adding the next. Mix in 1 teaspoon vanilla extract.

Combine wet with dates

Stir the mashed date mixture into the butter-sugar-egg mixture until evenly distributed.

Fold in dry ingredients

Whisk together 1 cup flour, 1 teaspoon baking powder, and 1/4 teaspoon salt in a separate bowl. Fold the dry ingredients gently into the wet mixture just until combined—do not overmix.

Bake

Spoon the batter into the prepared pan, smoothing the top. Bake in the preheated oven for 25–30 minutes, or until a toothpick inserted into the center comes out with just a few moist crumbs (the pudding should be set).

Rest in pan

Remove from the oven and let the pudding sit while you make the sauce (about 5 minutes). The cake will be hot; do not remove from the pan yet.

Toffee Sauce

Make the sauce

While the pudding bakes or immediately after removing it from the oven, combine 1/2 cup unsalted butter, 3/4 cup brown sugar, and 3/4 cup heavy cream in a small saucepan over medium heat. Stir constantly until the butter melts and the sugar dissolves.

Simmer and thicken

Bring the mixture to a gentle simmer and let cook for 4–6 minutes, stirring occasionally, until slightly thickened and glossy. Remove from heat and stir in 1 teaspoon vanilla extract and 1/8 teaspoon salt. Taste and adjust salt/sweetness if needed.

Pour over pudding

Pour about half of the hot toffee sauce evenly over the still-warm pudding in the pan, allowing it to soak into the surface. Reserve the remaining sauce for serving.

To Serve

Portion and finish

Scoop or cut portions of the pudding into bowls or plates. Spoon additional warm toffee sauce over each portion. Serve immediately with a scoop of vanilla ice cream or a dollop of clotted cream and sprinkle with chopped walnuts or pecans if using.

Storage

Store any leftover pudding and sauce in separate airtight containers in the refrigerator for up to 3 days. Reheat pudding portions gently in the microwave and warm the sauce on the stove before serving.