When it had started, Clef couldn't ever say. Like everything involving Umi that year, he was in the middle of it well before he'd even noticed it had begun.
The first notes had started out of curiosity more than anything else. The cakes Umi occasionally brought on visits fascinated him more than he would even admit to himself. They were so light and fluffy, and so very unlike the sorts of cakes and pastries that the cooks in Cephiro ever produced - even on special occasions. He just wanted to understand a bit more about how she could do that, and what made it possible.
It was a while before Clef actually started thinking about how one could manage to make something like it with Cephiran ingredients. Discussions about equivalent ingredients often became arguments or debates.
The concept of flour was one of the first things they started discussing. That had started back when Umi was asking her own questions about Cephiro's food. She'd commented on the nuttiness of the pawasute, the flatbreads, and was surprisingly startled to learn that the flour was made from the ground shells of taabo. Apparently, nut flours weren't particularly common in her world. Especially ones from the shell, not the inside. The inside of taabo was too soft to turn into a flour, but it was sometimes used in sweet fillings for pastries. Umi said it reminded her of one of the nuts she ate back home, if less crunchy.
Most of the flour Umi baked with came from grains. Some had properties that gave them a stretchy quality when a dough made from them was kneaded firmly, even. Which was something that taabo flour didn't have. There wasn't an easy way to make it turn into the soft, fluffy breads and sweet pastries that Hikaru sometimes brought. Taabo flour was better for things that didn't need much air to them, pastries and crunchy biscuits. It just didn't seem to catch the air in it like Umi said flour could, even when you beat it well. It still just wanted to be crunchy biscuits.
Despite flour being a possible roadblock, it was the concept of sugar that actually caused the worst of his trouble. Umi had spoken roughly of measurements of some things: two parts flour to one part sugar to so much milk. Only, he hadn't understood from her explanation that what she meant by sugar was not the sort of sweetener he was used to. Like most foods in Cephiro, all sweeteners came from a type of fruit. There were about five or six commonly used ones, but the one that everyone just referred to as 'sweetener' was a thick sweet syrup made from the little oiru fruits. It had a mild flavour and just added that soft touch of sweetness to a cup of tea, if you liked it.
When Clef learned that what Umi meant was actually dry, not wet, he realised why the last batter had been so sticky and barely salvageable as crisp sweet cakes.
Umi told him that oiru sweetener was more like something called honey than sugar, and he was so fascinated by the story of insects making a sweet syrup from the nectar of flowers that he failed to ask for any more detail about sugar until Umi's next visit when she brought a few paper packets of it to him. He had a little dish of the tiny sweet crystals on his desk for weeks after, and Umi laughed at him anytime she noticed it. Still, it got him thinking about the proportions of this mixture he was trying to make. If too much liquid was the problem, decreasing the sweetener would help, and in the end, he might manage a cake that Umi might actually want to eat.
His next attempt was practically edible. It was still very much not like cake. It was soft, but more in a sticky spongy sort of way, soggy and in need of being eaten with a spoon. It wasn't actually bad, so he made a detailed note of the results and planned to come back and alter it slightly for a different sweet desert. Perhaps something with a puragu jam center would be nice?
Undaunted, he kept toying with variations in his free time. His experiments littered the kitchen in the middle of the night when he couldn't sleep. Umi always said she used baking as a stress reliever. Clef could see how that might be the case if you knew what you were doing and had something to show for it, but learning the craft did not lend itself well to relaxation. Quite the opposite sometimes.
There may have been one or two new dents in the kitchen wall from where he'd thrown a spoon out of frustration.
One night he threw one so hard it sliced clean through the plasterwork, nearly taking out a shelf of teacups on the way. He rubbed his hands over his face.
What wasn't he getting?
For her birthday that year, Umi brought another of the fancy white cakes with the fruit that was like a miniature - and slightly tarter - version of puragu. Clef happily ate his share while Umi smiled at him over her cup of tea, her look not nearly as innocent as she might be pretending it was. In the midst of forcibly ignoring his body's reaction to that look, he tried to casually ask even more detailed questions about what made this cake just so airy and fluffy.
Umi explained the various powders used for baking, but they didn't make much sense and he was pretty sure his eyes just glazed over. "But for this sort of cake, you don't use any of that, you just whip a few extra eggs until they are really light and fluffy, then fold everything else in as carefully as possible, so you don't lose any of the air."
"Eggs?" Clef asked, nearly dropping his fork as he stared at her, then the cake, and then back at her.
"Usually chicken eggs," Umi set down her cup to try to show how big the eggs were, but Clef was too busy trying to understand that all the sweets and cakes and things that she had brought from Tokyo all used egg in them.
"Why would you use an animal's eggs in so much of your baking?"
She blinked at him, opened her mouth, then shut it. She lifted a hand and opened her mouth again. "They're not -" she started, her eyebrows knitting together as she seemed to search for the words. "They've not been fertilised. The eggs, that is. It's not like I'm taking some bird's young."
"Oh," Clef breathed.
"From what I know, chickens will lay eggs whether or not they've mated, so you end up with a lot of eggs that would do nothing but rot, so… you eat them? They're nice fried. Oh, you can also scramble them up and fry like a pancake of egg and wrap it around rice." Umi rubbed the back of her head as she let out a soft laugh. "Sorry. I forget that you don't always eat the same sorts of things here. I mean, I should remember that given your milk comes from a fruit and cheese grows on the ground like a pumpkin. Maybe I just thought you had something else that could stand in for egg…"
Clef picked back up his plate and went back to eating. He personally thought it was strange that milk in Tokyo came from animals, not from fruit, but Umi had just laughed at him when he tried to argue about that sort of milk being for babies, because it was only babies in Cephiro who were ever fed milk from another animal, because they couldn't nurse from their parent for one reason or another. Uinka juice didn't have the right sort of nutrition to feed a growing person, despite tasting nice. Now was probably not a good time to start that debate again.
While he wasn't going to go out and try to find some sort of creature to lend him an egg or three for his experimentation, that conversation did give Clef another idea of where to go for possible answers.
Before leaving the castle for the week, he ventured down to the kitchens to ask the chefs if they knew of anything that could approximate what Umi described eggs doing, something that when whipped with a whisk would go light and airy. There were a few old-fashioned dishes he remembered being whipped until they were light and airy, but he couldn't remember what went into them. He hadn't been spending much time in a kitchen at that point, so never took any notice.
The answer he was given was kaabon, a funny little root that needed to be grated up into a paste and them whipped with maybe half as much uinka juice to become a fluffy pudding sort of thing. If he mixed that with the flour, sweetener, and some vegetable fat, he might just be able to get something more like cake.
And indeed he did. It wasn't perfect, but it at least could be cut with a knife and eaten with a fork.