Preheat the oven to 350F.
Separate the egg whites from the yolks. Then, divide the sugar into two portions: 75g and 25g.
Add the cream of tartar to the bowl with the egg whites. Beat the mixture until it becomes foamy, similar to cappuccino foam. Gradually add 75g of sugar while continuing to whip the egg whites until the mixture forms stiff peaks.
Mix the egg yolks with the remaining sugar, room temperature earl grey milk, neutral oil, and vanilla extract. Next, sift in the flour, baking powder, and tea leaves. Stir everything together until well combined.
Gently fold one-third of the egg white mixture into the egg yolk mixture until the batter lightens. Then, gradually fold in the remaining egg white mixture, one-third at a time, until the batter is pale and light.
We are making a 3 tiered cake, so evenly distribute the batter amongst three 5" silicone cake mold and place them on a baking sheet. Bake for 25-35 minutes or until the sponge has turned a golden brown and a toothpick inserted comes out clean. Remove the cakes from the oven. Carefully pick up each mold and drop it against the baking sheet to help loosen the edges and preventing the cake from deflating in the center. Let it cool for 2-3 hours. After the cake cools, you can move onto assembling the cake. You can also refrigerate the cake and assemble it later.