CHOCOLATE SPONGE:

1. Combine flour, baking powder, and cocoa powder in a bowl. Set aside.
2. Beat butter and sugar until fluffy. Add egg yolks one at a time. Beat in milk.
3. Add flour mixture. Mix just until incorporated — do not overmix.
4. Pour into a greased and floured 9×13-inch (23×33 cm) cake pan and bake for 18–20 minutes in a preheated 350°F (175°C) oven.
5. Combine the brewed tea with the rum. Pour the tea mixture evenly over the hot cake. (You do not need to wait for the cake to cool before doing this.)

MARSHMALLOW TOPPING:

1. Beat egg whites to stiff peaks. Add sugar and beat a little more.
2. Place the mixture over a double boiler and cook, stirring constantly, for 4–5 minutes. The mixture should be hot but the egg whites should not curdle.
3. Pour over the cake (still warm is fine) and smooth with a spatula. Let cool completely before adding the glaze.

CHOCOLATE GLAZE:

1. Melt the chopped chocolate with the vegetable shortening in a double boiler or microwave in 30-second bursts, stirring between each, until completely smooth.
2. Pour the glaze over the cooled cake and spread evenly. Allow to set at room temperature or refrigerate for 15 minutes to firm up.