1Preheat oven to 150°C (300°F). Line an 8x8 inch baking tray with parchment paper.
2In a large mixing bowl, combine all purpose flour, sugar, cocoa powder, baking powder, and baking soda.
3Add the egg, oil, milk, warm water, instant coffee, and vanilla extract to the dry ingredients. Mix well until smooth.
4Pour the batter into the prepared baking tray.
5Bake for about 30 minutes, or until a toothpick inserted into the center comes out clean.
6Remove from oven and transfer the cake to a wire rack to cool completely.
7For the topping, chop the chocolate into small pieces. Gently warm the heavy cream and pour it over the chocolate. Let sit for a minute, then mix until smooth. If the chocolate is not fully melted, microwave for a few seconds at a time, stirring in between, until fully melted.
8Spread the chocolate topping evenly over the cooled cake.