Preheat the oven to 180°C/350°F (without fan).

Grease and flour a large bundt pan with approximately 2 litres (8 cups) capacity. (See Kitchen Notes below)

Sift the flour, baking powder, and salt into a large bowl.

Using a stand mixer or electric beaters, cream the butter and sugar until the mixture is pale and fluffy. This should take about 3-5 minutes on medium-high speed.

On low-medium speed, add one egg, followed by a tablespoon of the flour mixture. This helps to prevent the mixture from curdling. Beat until the egg has been incorporated. Repeat until all of the eggs have been added.

Add the vanilla extract and milk.

Add the remaining flour mixture and beat lightly until all of the ingredients have been incorporated.

Remove slightly more than half of the batter to another bowl. This portion will form the vanilla batter for the marble cake.

Add the cocoa powder to the bowl with slightly less than half the batter, and mix it through. This portion will form the chocolate batter for the marble cake.

Dollop half of the vanilla batter into the prepared bundt pan.

Next, pour in all of the chocolate batter. At this stage, don't worry about spreading the cake batter evenly.

Dollop the remaining vanilla batter onto the chocolate layer, and use a small palette knife to smooth out the layer.

Tap the bundt pan gently on the kitchen surface once or twice to make sure that the batter settles into all of the grooves of the bundt pan. This tapping motion also helps to gently mix the batter to form a marbled pattern inside the cake.

Place the cake pan into the oven and bake (without oven fan) for 35-50 minutes, or until a cake skewer inserted in the thickest part of the cake comes out clean. The baking time will vary depending on the size of your cake pan and your oven.

Once the cake is cooked, let it rest in the cake pan on a wire rack for 10-15 minutes.

Carefully turn the cake out onto a wire rack and let it cool completely.

To make the chocolate glaze, whisk together the icing sugar (powdered sugar), cocoa powder, milk and vanilla extract. Depending on how thick you want the glaze to be, you may not need all of the milk. If the glaze is too runny, simply thicken it with some more icing sugar (powdered sugar).

Once the cake has cooled completely, drizzle the glaze over the cake.

Leave it for at least 30 minutes to set before serving.