Preheat oven to 170°C (340°F) or 150°C (300°F) for fan-forced ovens. Line and grease the base (not the sides) of a round 20cm (8in) baking tin with baking paper (parchment paper)
Make sure your stand mixer bowl and balloon whisk are free from fat. To do this, lightly dampen a paper towel with white vinegar or lemon juice and wipe the inside of the bowl and all over the whisk.
Use 3 bowls to separate the eggs. One bowl to collect the yolk, one to collect the whites and one for separating the egg. Doing this will help prevent contamination of the whites if a yolk breaks. A tiny amount of yolk can prevent the whites from whipping up.
In a large bowl, combine the yolks, milk, oil and vanilla extract and whisk until smooth. Sift in the flour and salt into the mixture and whisk again until there are no clumps. Set aside for later.
Pour the egg whites into the stand mixer. Start at slow speed, then gradually increase to medium-high. Once foam forms, drizzle in the sugar very slowly. Once the sugar is all in, increase the speed to high. Whip the whites until it reaches medium to firm peaks. This is when the whites should be stiff enough to stand up firmly but have a little curl at the tip when you lift the whisk.
Place a third of the egg whites into the batter and whisk until smooth. Add another third of the egg whites and gently fold it through the batter with a spatula. Take care not to remove the air from the egg whites. Once incorporated, gently fold in the remaining egg whites. The combined batter should look airy but smooth.
Pour the batter into the tin. Tap the tin against the kitchen bench a few times to remove air bubbles. Place the cake tin into a larger baking tin and pour in boiled water until it reaches approximately 2cm (.8in) from the base of the cake tin. Bake for 45 to 50 minutes or until a skewer comes out clean when inserted in the middle of the cake.
The cake will deflate a little once it's out of the oven with little wrinkles on the top. Don't worry because the decorations will cover it up and it won't affect the taste or texture of the cake. Leave the cake to cool in the tin for ten minutes, then run a blunt knife or an offset spatula around the sides of the cake. Turn the cake onto a cooling rack and allow it to cool completely.
Once the cake has cooled, carefully use a bread knife or a cake leveller to cut the cake into 3 even layers. Peel the mangoes and cut 3 cheeks roughly into 1cm cubes (.4in) For the mango slices, use a sharp knife to cut thin slices. Lay the slices on a chopping board or plate and set them aside. Depending on the size of the mangoes, you may need more or fewer slices and cubes.
Place cream, vanilla extract and icing sugar into the bowl and whip at high speed until the cream is fluffy and holds its shape. Divide the cream evenly in two separate bowls. Add a few drops of yellow food colouring into one bowl and fold gently until the colour is even.
Place a layer of cake on a cake stand or board. Spread the white cream over the cake with a spatula, then place half of the diced mangoes on top. Cover the mangoes with more cream, then place on another layer of cake. Repeat the same process for the next layer. Use the yellow cream to cover the entire outside of the cake. Smooth it out evenly, but don't worry if it doesn't look perfect as the mangoes will cover the sides. Optional - leave approximately 1/2 cup of cream to pipe around the base of the cake.
Place the large slices of mangoes on the side of the cake, overlapping them slightly. The cream should help hold them in place. Use the smaller slices of mango for the ears, however, you may need to trim them to the right size and shape. Do the lion's face just before serving or the black icing may run and ruin the look of the cake. Shape the black icing with your hand. Make two flat circles for the eyes and a long triangle for the nose. Use an icing gel to draw on the whiskers. Optional - Place the remaining yellow cream into a piping bag and pipe around the base of the cake.