Preheat oven to 165 °Celsius.
Add the milk and sour cream to a small bowl and whisk until smooth. Set aside.
In a medium-sized bowl, beat butter and brown sugar until light and fluffy for about 2 minutes. Scrape the sides of the bowl halfway through.
Add the eggs, one at a time. Beat until the traces of the egg are no longer visible. Scrape the sides of the bowl.
In a separate bowl, sift the flour, cocoa powder, baking powder, and salt. Fold in the sifted ingredients into the creamed mixture in three batches. Alternate with the milk-sour cream solution in two batches.
Finally, add in vanilla essence and combine well. Pour batter into a well-greased and floured loaf tin measuring 8 inches by 4 inches and bake for 50 to 55 minutes. Test the cake at 50 minutes baking time by inserting a skewer in the center of the cake. The cake is done if the skewer comes out without any wet batter.
Remove the cake from the oven and let it rest in the tin for 5 minutes before turning it out onto a wire rack to cool completely. Place the cake facing up on the rack.
To make the chocolate glaze, double boil (or microwave) the cream until the sides start to bubble.
Remove it from heat and pour it onto the chopped chocolate. Let it sit for a few minutes before stirring. Mix until it becomes a smooth glaze. Let ts cool down until it reaches a slightly thick consistency.
Spread the glaze generously on the cooled cake top. Use a spoon to gently push the glaze to drip around the sides of the cake.