Preheat the oven to 350°F (175°C). Line a loaf pan with parchment paper.
Add the softened butter to a mixing bowl.
Add the condensed milk and mix well until combined.
Add the sugar and continue whisking until the mixture is smooth.
Add the eggs, milk and whisk until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture. Gently mix until a smooth batter forms, avoid overmixing.
Fold the dark chocolate chunks into the batter until evenly distributed.
Add the cocoa powder and whisk until the batter is evenly chocolate-colored.
Transfer the batter to the prepared loaf pan and spread it evenly.
Bake for 45–55 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Remove the cake from the oven and allow it to cool in the pan for a few minutes.
Slice the cooled cake.
Arrange the sliced cake on a serving plate and enjoy.
