Preheat your oven to 180°C (160°C Fan, 350°F).

In a small bowl, mix 1 tablespoon of plain white flour, vegetable shortening, and vegetable oil to create a smooth paste for greasing the bundt tin.

In a large bowl, mix white caster sugar and baking margarine until pale and creamy (3-5 minutes).

Add eggs one at a time to the mixture, whisking thoroughly after each addition.

Sift in self-raising flour and cocoa powder; gently fold them into the mixture.

Fold in whole milk to loosen the batter.

Spoon the batter into the prepared bundt tin, filling about three-quarters full.

Bake for 35-40 minutes or until a skewer inserted in the center comes out clean.

Let the cake cool in the tin for about 10 minutes, then turn onto a wire rack to cool completely.

In a bowl, whisk together icing sugar, cocoa powder, and milk until smooth and glossy.

Pour the icing over the cooled cake and top with chocolate mini eggs and halved creme eggs.