Heat your oven to 180°C or 160°C fan.
Line your baking tray with parchment paper carefully.
Grease the paper with a little butter.
This helps the cake come out easily later.
Beat butter and sugar until light and fluffy.
This takes about 3 minutes with electric mixer.
Add eggs one at a time slowly.
Beat well after adding each egg to mixture.
Sift flour, cocoa powder, and baking powder together.
Fold these dry ingredients into your wet mixture.
Add milk and mix until just combined smoothly.
Don't overmix or cake becomes tough and dense.
Pour batter into your prepared baking tray evenly.
Spread it out with a spatula gently.
Bake for 30-35 minutes in preheated oven.
Check with a skewer inserted in center.
It should come out clean when cake is done.
Melt chocolate and butter together in a bowl.
You can use microwave or double boiler method.
Stir in milk until mixture becomes smooth.
Let it cool for 5 minutes before using.
Let cake cool completely on a wire rack.
Spread chocolate icing evenly over the top surface.
Cut into squares or rectangles as you prefer.
Serve and enjoy with your loved ones.