Preheat the oven to 180 C (350 F) and prepare your baking pan. I used a loaf tin (around 23x13 cm, or 9x5 inch), and lined it with parchment paper. A regular 23x23 cm (9x9 inch) tin will work fine as well.
In a small bowl, stir together the chopped dates and hot coffee and set aside. If you're not a fan of coffee, use hot water instead.
In another bowl, combine the flour, cocoa powder, baking soda, baking powder and salt, then set aside.
Beat together the butter, treacle or molasses and brown sugar together until creamy and light.
Gradually beat in the eggs and vanilla extract.
Alternate the date and flour mixture. Start by adding in ½ of the flour mixture, followed by the date mixture, followed by the rest of the flour mixture.
Pour the batter into the prepared baking tin and bake for 45-55 min or until a toothpick inserted comes out clean.
Let the cake cool for about 30 min to an hour, then pierce it all over, using a skewer or chopstick. This ensures that the cake will absorb all of the toffee sauce.