Add dates and baking soda to a blender, pour in boiling water from a tea kettle, and blend from low to high until smooth. Start slow so the hot, sticky mixture does not erupt.

Cool the date puree below the melting point of butter, about 100°F.

Add sugar, eggs, vanilla, salt, and cold butter, then blend on high until smooth and emulsified.

Reduce blender speed to a steady vortex, then pour the flour and baking powder into the center of the vortex to avoid it sticking to the sides of the pitcher, then blend just until combined.

Pour batter into a nonstick rice cooker bowl. If the bowl is not nonstick, butter and flour it first.

Cook on cake mode until the center is above 185°F, about 1 hour. Use porridge or steam mode if cake mode is unavailable.

Cool the cake fully to room temperature, or chill until cold. Slap the side of the bowl firmly to loosen the cake, then invert onto a plate.

Microwave dark muscovado sugar, butter, and cream in the empty rice cooker bowl for 1 minute. Stir until the butter melts and the sugar dissolves, then stir in whiskey.

Return the cake to the bowl, browned side down, so it can soak up the toffee. Put the bowl back in the rice cooker and hold on keep warm mode until ready to serve.

Invert the cake onto a serving plate and finish with flaky salt. Serve with an extra batch of toffee on the side for a more generously sauced pudding.