Preheat oven to 350°F (175°C) and grease a baking dish.
In a bowl, combine flour, cocoa powder, baking powder, and salt.
In a separate bowl, cream together butter and brown sugar until fluffy.
Beat in eggs and vanilla extract, then fold in the dry ingredients to form a smooth batter.
Stir in chopped dates or optional chocolate chunks. Pour batter into the prepared baking dish.
Bake for 25–30 minutes until a skewer comes out clean.
Prepare toffee sauce by melting butter with brown sugar and cream in a saucepan; bring to a simmer.