Heat the milk from the egg yolk batter until boiling, cut open one tea bag and pour it in, and steep the other tea bag directly. Turn off the heat and let it cool, then remove the steeped tea bag. * For a stronger tea flavor, cut open both tea bags and pour them into the boiling milk.

Mix the egg yolks, sugar, and vegetable oil, then add the cooled milk tea from step 1 and mix well.

Sift the flour and cornstarch into the egg yolk milk tea mixture and mix until smooth. * You can substitute the combined amount of all-purpose flour and cornstarch with cake flour.

Beat the egg whites until foamy, then add lemon juice. Gradually add sugar in three parts, beating until stiff peaks form.

Fold some of the meringue into the egg yolk batter, then pour the egg yolk mixture back into the remaining meringue and fold gently.

Pour the mixed cake batter into a non-stick cake pan. Bake at 300°F (150°C) for 45-50 minutes. * The cake is done when a skewer inserted into the center comes out clean.

Invert the baked cake to cool completely.

To make the milk tea custard: Mix the egg yolks, sugar, and cornstarch until smooth.

In a separate pot, heat the milk, vanilla extract, and tea bag until small bubbles form around the edges.

Remove the tea bag, pour the hot milk tea into the egg yolk mixture, and mix well. Strain twice, then return to the stove and heat on low, stirring until thickened, then remove from heat.

Pour the milk tea custard into a dish, smooth the surface, cover with plastic wrap touching the custard, and refrigerate until needed.

Run a flat spatula around the edge of the cake pan and the center tube to release the cake carefully.

Add 2 tablespoons of extra sugar to the heavy cream, then fold the custard into the cream and beat until slightly thick but still pourable. Pour into the hollow center and over the top of the cake. Finally, top with cooked tapioca pearls.