Preheat oven to 350°F.
Finely chop the dates. You should have about 1 cup loosely packed. Place the dates in a bowl and cover with boiling water and sprinkle with baking soda. Stir, then allow the mixture to sit undisturbed for 20 minutes.
Meanwhile, using a hand mixer or stand mixer fitted with the paddle attachment, beat butter, brown sugar, and molasses until creamy and combined. Add the eggs, one at a time, beating well between each addition and scraping the sides and bottom of the bowl as needed. Beat in the vanilla.
In a separate bowl combine flour, baking powder, and salt. Add the flour mixture into the butter mixture and beat until combined, scraping the sides and bottom of the bowl as needed.
After the dates have soaked for 20 minutes, mash or puree the dates along with the liquid. If the dates you used were moist you should be able to mash them easily with a fork. If the dates were really dry it will likely be easier to use an immersion blender or small food processor to puree (they don't have to be completely smooth). Transfer all of the date mixture into the cake batter and beat until combined.
Grease ramekins** or a 12-count muffin tin (see note for an 8x8 pan). Transfer the batter to the prepared pans and smooth the top. Bake until a toothpick inserted into the center comes out clean. Depending on the size of your ramekins this can be anywhere from 20-25 minutes. Be careful not to overbake. Place on a wire rack to cool.