For the cake:
Butter, for baking dish plus 1/4 cup, melted
Scant 1/3 cup dark brown sugar, packed
1 cup plus 2 tablespoons self-rising flour
1/2 cup whole milk
1 egg
1 teaspoon vanilla extract
3/4 cup plus 2 tablespoons chopped, rolled dates
For the sauce:
3/4 cup dark brown sugar, packed
Approximately 2 tablespoons unsalted butter in little blobs
2 1/4 cups boiling water
For the cake:
Preheat the oven to 375 degrees F and butter a 1 1/2-quart capacity baking dish.
Combine the sugar with the flour in a large bowl. Pour the milk into a measuring cup, beat in the egg, vanilla and melted butter and then pour this mixture over the sugar and flour, stirring with a wooden spoon to combine. Fold in the dates then scrape into the prepared baking dish. Don't worry if it doesn't look very full; it will by the time it cooks.