Preheat oven to 350°F. Lightly grease 6 ramekins or a muffin tin.
In a bowl, pour boiling water over chopped dates. Stir in baking soda and let sit for 10 minutes.
In a separate bowl, cream butter and brown sugar until fluffy. Beat in eggs and vanilla.
Stir in soaked date mixture (it’s okay if it looks a bit lumpy).
Fold in flour, baking powder, and salt until just combined.
Divide batter into ramekins. Place on a baking sheet and bake 18–22 minutes, or until puffed and springy.
While cakes bake, make the sauce: Combine butter, cream, and brown sugar in a saucepan. Bring to a simmer and cook for 3–5 minutes, stirring until smooth. Stir in vanilla.
Let cakes cool slightly, then invert onto plates and pour warm sauce generously over each.