Beat the sugar with the softened butter until the mixture is pale and all the sugar crystals have dissolved. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.

Gradually add the self-rising flour, alternating with the milk. If the batter is too thick, add a little more milk. Mix well until smooth.

Divide the batter into two equal parts. Add the cocoa powder to one part and mix well.

Line the inside bottom of the milk carton mold with a piece of parchment paper or regular white printer paper. Grease both the mold and the paper with oil, then dust with flour. Fill the mold by alternating spoonfuls of the chocolate and vanilla batters. This recipe makes two small loaves.

Bake in a preheated oven at 300°F (150°C) for about 30 minutes, or until a knife or toothpick inserted in the center comes out clean. Enjoy!