Put the chopped dates in a heatproof bowl. Pour the boiling water over them, stir in the baking soda, and let sit for 10 minutes. The mixture will become thick and slightly puréed; mash lightly with a fork if needed to break up large pieces.

Preheat and prepare pan

Preheat the oven to 180°C (350°F). Butter an 8-inch (20 cm) square baking dish or six individual ramekins (about 6–8 oz each) and set aside.

Cream butter and sugars

In a mixing bowl, beat the softened butter with the light brown sugar and granulated sugar until pale and fluffy, about 2–3 minutes. Scrape down the bowl as needed.

Add eggs and vanilla

Beat in the eggs one at a time, fully incorporating after each addition. Mix in the vanilla extract.

Combine dry ingredients

Whisk together the all-purpose flour, baking powder, and salt in a separate bowl.

Combine wet and dry

Fold about one-third of the dry mixture into the butter-egg mixture to lighten it. Add half of the date mixture (including any loose liquid), fold gently, then repeat with another third of the dry mix. Finish with the remaining dry ingredients, folding until just combined. Do not overmix.

Bake

Spoon or pour the batter into the prepared dish or ramekins and smooth the tops. Bake in the preheated oven for 25–30 minutes for a square dish, or 18–22 minutes for individual ramekins, until the tops are set and a skewer inserted into the center comes out with moist crumbs (not wet batter).

Rest

Remove from the oven and let rest for 5 minutes while you make the sauce. If using ramekins, you can serve directly in them or turn out onto plates.

Toffee Sauce

Melt butter and sugar

In a small saucepan over medium heat, combine the butter and light brown sugar. Stir constantly until the sugar dissolves and the mixture starts to bubble gently, about 2–3 minutes.

Add cream and simmer

Carefully add the heavy cream (mixture will steam and bubble). Stir and bring to a gentle simmer. Let simmer for 3–5 minutes, stirring, until the sauce thickens slightly and coats the back of a spoon.

Finish sauce

Remove from heat and stir in the vanilla extract, optional rum or brandy, and a pinch of sea salt. Taste and adjust salt or alcohol level as desired. Keep warm until ready to serve.

To Serve

If the pudding was baked in a square dish, cut into portions and place on warm plates. Spoon a generous amount of warm toffee sauce over each portion and serve immediately with a dollop of double cream, or a scoop of vanilla ice cream. For individual ramekin servings, spoon sauce over each ramekin (or invert onto plates and pour sauce over).

Optional: Scatter a few flaky sea salt crystals over the top of the sauce for contrast, and serve with extra sauce on the side.