Chop the dates and place them in a heat-safe bowl. Add the baking soda and cover the dates with boiling water. Allow them to sit for at least 5 minutes to soften, then blend the dates and all the liquid in a food processor until smooth.

In the meantime, grease a standard-sized muffin tin with butter and flour, tapping out the excess, and set aside**. Preheat the oven to 350℉.

Sift the flour, baking soda, and salt into a bowl and set aside.

In a separate bowl, beat the butter and dark brown sugar until light and fluffy. Add in the egg and vanilla until well incorporated. 

Fold the dry ingredients into the wet mixture, being careful not to overmix. Right before all of the flour is incorporated, fold in the pureed dates until evenly distributed.

With a cookie scoop or spoon, evenly distribute the cake batter into the muffin tins until almost full (around ¾). 

Bake the puddings for 18-20 minutes (or 45-50 minutes for an 8x8 pan), until a toothpick comes out clean. In the meantime, make the toffee sauce.

Place the butter, dark brown sugar, corn syrup, molasses, and vanilla in a pot over medium heat until the sugar is dissolved and the mixture is bubbling (you shouldn't be able to feel any sharp granules of sugar in the mixture). Reduce the heat and gradually add the cream, whisking constantly. Cook the sauce for 1 minute more, until it begins to thicken slightly. Remove the saucepan from the heat, stir in the salt to your preference, and set aside.

Once the puddings are done baking, immediately pierce them all over with a fork or toothpick. Pour the toffee sauce over the puddings while they're still warm. Allow them to soak at least 5 minutes before removing from the pan and serving.