SPONGE: Combine flour, cocoa powder and baking powder.Whisk egg
whites and set aside. Mix egg yolks with sugar until pale. Add
vanilla extract, egg whites and flour-cocoa mixture. Slowly and
gently stir with a spoon (do not use mixer).
Transfer the mixture to a sheet pan lined with baking paper (my pan
is 12x13 inches or 30x33 cm large). Bake in 180 C (350 F) oven for
about 15 minutes.
Roll the sponge together with baking paper and let cool.
FILLING: Mix eggs with sugar over water bath (or a very low heat).
Cook until mixture reaches 80 C (175 F). Be careful, because if you
continue cooking over this temperature, the eggs will coagulate
(scramble).
Add chocolate, coffee powder, vanilla extract and rum. Let cool to
room temperature. Mix butter until fluffy. Combine butter with
egg-chocolate mixture.
ASSEMBLING: Peel off the baking paper from the sponge. Place on a
cling film (it will help you roll the cake easier). Spread the cake
with 1/2 of the chocolate filling. Place two bananas on 2 opposite
sides of the cake. Slowly roll each end toward center.
Spread remaining filling on the top of the cake roll. Use a fork to
create lines (if not using whipped cream).
OPTIONAL STEP: Before serving, take the cake out of refrigerator and
let come to room temperature. Whip cream until stiff. (If cake will
wait for your guests for longer time, consider stabilizing whipped
cream.) Sprinkle with chocolate sprinkles.
Original recipe does not contain whipped cream and chocolate
sprinkles, but I like to decorate Chocolate Banana Swiss Roll this
way.
