Custom baking: what ingredients do in a cake

There's chance that these guys will rise

Do you ever wonder how things work? How come a CRT screen while showing black is still emitting light? Why does it make sound when I crack my knuckles? What is yawning all about? What does milk do in a cake and why does it take a whole cube of butter to make the battenberg cake?

We don't live in the ol' days of analog knowledge where you either had to pick up a huge book and (gasp!) flip pages until you found the answer, or ask your grandma (because they sure know a lot). Anything you want to know is just a Google search away. I've recently pondered, as I closed door to the oven and saw an unopened bottle of milk and remembered that I forgot to add it to the batter, what is milk good for in a cake anyway? The batter was gooey enough and the cake turned out alright in the end, only perhaps a bit too crumbly.

Battenberg cake

Recently, I have been exposed to a chocolate bar that had two colors - a pink one and a white one. It reminded me of a cake I made almost two years ago. It too mixed pink and white and what's more, it was coated in a delicious layer of apricot jam and marzipan.

Today, I tried making a slightly modified Battenberg cake, using 70% of a traditional recipe with some ingredients (rum and coconut) that you normally don't find in it. Also I used different coloring since Prague decided not to have any shops selling food coloring open on weekend and they had only yellow at Tesco. Durrr.
Anyway, for my version, I used a high quality marzipan that was both expensive and sold in small packages. That's why my layer of marzipan is so thin. It should be thicker like on the last picture (that's the one I made years ago) but it doesn't really matter since it's there mainly to hold the constructed cake together. And one more thing, it might not be a bad idea putting more than 4 spoons of rum in it. Its taste was almost indistinguishable and the aroma was merely slightly there.