Preheat the oven to 350℉ (180℃).

Spray the baking pan with cooking spray.

Separate the egg whites from the egg yolks.

Beat the egg whites with an electric mixer until stiff peaks form. Set them aside.

In another bowl, use an electric mixer to beat the egg yolks with the sugar until the mixture is pale and thick.

Add milk and oil to the egg yolk mixture. Mix it well.

Add flour and baking powder, and mix until smooth.

Add the cocoa powder, and mix until fully incorporated.

Using a wooden spoon, gently fold in 3 tablespoons of the beaten egg whites to lighten the batter. Then, slowly fold in the remaining egg whites until just combined. Be careful not to deflate the mixture.

Pour the batter into the prepared baking pan and bake for 25 minutes. Check for doneness by inserting a toothpick into the center; if it comes out clean, the sponge is done.

Immediately after removing the sponge from the oven, spread your favorite jam over the top, then return the sponge to the oven for 5 minutes.

After removing the sponge from the oven, quickly place 12 marshmallows on top and return it to the oven for no longer than 5 minutes. Remove it when the marshmallows start to melt and turn a pale golden brown.

Place one additional marshmallow on top of each melted marshmallow.

Let the sponge cool down completely.

Once cooled, use the black decorating icing to draw faces on the marshmallows.