This classic South African dessert capitalizes on a moist texture and a rich, intoxicating flavor. Pudding is something of a misnomer; it's actually a cake by American standards. Be sure to choose good-quality brandy, as it makes a real difference in the flavor of the cake.
Position a rack in the lower third of the oven, and preheat to 350 degrees F. Butter a 7x11-inch baking pan and set aside.
Place the dates and pecans, if using, in a small bowl and add the boiling water. Stir in the baking soda and salt and let the mixture sit until cool.
Meanwhile, place the butter and brown sugar in a mixing bowl and beat with an electric mixer until creamy. Add the eggs, vanilla, and allspice, and beat until the mixture is smooth and fluffy, about 3 minutes.
In another bowl, whisk together the flour and baking powder. Add the flour mixture to the bowl with the butter-egg batter and mix to combine at low speed. Add the date-pecan mixture and stir until just combined.
Pour the batter into the prepared pan and bake until the cake is set in the center, firm to the touch, and the edges have begun to pull away from the sides of the pan, 30 to 40 minutes.
While the cake is baking, prepare the sauce. Combine the water, 1 cup of sugar, and butter in a small pan and bring to a boil over high heat. Cook until the mixture turns syrupy, 3 to 5 minutes. Remove the pan from the heat and let the sauce cool for 10 minutes before stirring in the brandy and vanilla.
Remove the cake from the oven and pour the sauce over the hot cake. Let the cake sit until the sauce has soaked in. To serve, cut into squares and serve warm with a dollop of whipped cream.