Preheat the oven to 350F. Generously grease 2 (14-ounce) or 4 (8-ounce) ramekins with butter; set aside.

In a small bowl, combine the dates and baking soda. Heat the milk in the microwave for ~1 minute until hot. Pour the hot milk over the dates and stir. Let sit for 10 minutes, or until cool and the dates have softened.

Once softened, use an immersion blender or pour the mixture into a blender to blend into a paste. Set aside.

In a small bowl, whisk together the flour, baking powder, espresso powder (if using), and salt. Set aside.

In a separate medium bowl, combine the cocoa powder with the hot water. Whisk until a thick paste forms.

Add the softened butter, brown sugar, and vanilla. Beat until well combined.

Add the date paste mixture, egg, and egg yolk. Whisk until well combined.

Add the flour mixture to the wet mixture, and fold to combine until the batter is smooth.

Scoop and divide the batter evenly into the prepared ramekins.

For 8-ounce ramekins: bake at 350F for 28-33 minutes. For 14-ounce ramekins: bake at 350F for 35-40 minutes, until just firm when pressed in the center.

While baking, prepare the chocolate sauce. Add the heavy cream, chocolate chips, butter, brown sugar, cocoa powder, and salt to a medium saucepan over medium heat. Stir and cook until all of the butter and chocolate have melted, and the sauce is smooth.

Remove the cakes from the oven. Use a skewer or fork to poke holes in the cakes. Spoon about half of the chocolate sauce over the cakes and allow to soak for a few minutes.

Invert the cakes onto plates. Serve warm with a scoop of vanilla ice cream and an extra drizzle of the chocolate sauce.