Place the chopped Medjool dates in a heatproof bowl. Pour the boiling water over them and let them soak for 5 minutes.
Pulse the softened dates and soaking liquid briefly in a food processor until nearly smooth. Alternatively, mash them thoroughly with a fork.
Stir the baking soda into the date mixture, then set it aside while preparing the cake batter.
Preheat the oven to 350°F (175°C). Lightly grease a 12-cup muffin tin, individual ramekins, or an 8-inch square baking pan.
In a large mixing bowl, beat the softened butter and light brown sugar until pale, light, and fluffy.
Add the eggs one at a time, beating well after each addition. Mix in the molasses and vanilla extract until evenly combined.
In a separate bowl, sift together the all-purpose flour, baking powder, and salt.
Gently fold the dry ingredients into the butter mixture until just combined. Fold in the prepared date mixture, including all the remaining soaking liquid. Avoid overmixing.
Divide the batter evenly among the prepared muffin wells or ramekins, or spread it evenly in the square baking pan.
Bake individual puddings for 18–20 minutes or bake an 8-inch square pudding for 22–25 minutes. The pudding is ready when a toothpick inserted into the center comes out clean or with a few moist crumbs.
While the pudding bakes, combine the heavy cream, butter, light brown sugar, and salt in a medium saucepan over low heat.
Cook for 7–10 minutes, stirring constantly, until the sugar has completely dissolved and the sauce has thickened slightly.
Remove the saucepan from the heat and whisk in the vanilla extract.
Invert the warm individual puddings onto serving plates or cut the square pudding into portions. Spoon a generous amount of warm toffee sauce over each serving and enjoy immediately.