Preheat the oven to 350°F (175°C). Grease and line an 8-inch (20 cm) square pan with parchment paper extending over the sides.

In a small pot bring the dates and water to just below a simmer (about 2 - 3 minutes - or until small bubbles start to form on the surface)

Remove from heat and let cool for 15 minutes.

Purée (or mash) the dates with the water and transfer the mixture to a large bowl.

Whisk sugar, oil and egg into the puréed dates until combined.

Sift in the all purpose flour, unsweetened cocoa powder, baking powder, salt and ground cinnamon (see notes 2 and 3 )

Mix to form a smooth thick batter.

Pour the batter into the lined baking pan

Bake for 30-35 minutes, until a toothpick or cake skewer inserted in the center of the cake comes out clean.

Remove the cake from the oven but leave the cake in the pan for 10 minutes. Then transfer the cake to a wire cooling rack to cool completely before frosting.

Beat the butter and half of the powdered sugar (icing sugar) until crumbly (about 1 minute on medium speed)

Add milk and the remaining half powdered sugar (icing sugar) and beat on medium speed for another minute or until it has a thick smooth texture.

The frosting (icing) may seem like it's not enough when you first mix it, but it actually spreads evenly over the entire cake—it's just the right amount.

Slice into squares to serve.