Backstory (skip if desired)
Let's take our cute and self-conscious protagonist, Jayden! (For the people that read and responded to the post about the genetics behind keidran and the colonization of the Ilus system, they are in one and the same universe.)
He's your average starship engineer in all ways except he's a fox keidran. (Although not too long ago he wasn't fluffy.) This came with lots of problems, mostly trying to get used to being a keidran, and the rest being the fact that he can't get his hot chocolate. Completely devastating. How do you expect 'em to fix a derelict dyson swarm without his hot chocolate?
As we know, chocolate is toxic to dogs, and by extension, dog-people. The thing that makes chocolate toxic is a combination of caffeine, and theobromine. But before we handle that, let's start with an example keidran for testing.
(Image Credit to TwoKinds Author Tom Fischbach.)
Let's start with the familiar half of the equation. Caffeine. According to wikipedia, caffeine is a central nervous system stimulant. It is mainly used recreationally as a cognitive enhancer, increasing alertness and attentional performance.
One side affect is that it behaves similarly to adrenaline by increasing heart rate, and thus exasperating cardiovascular issues, like heart attacks.
The other side of the equation, theobromine. It's the principal alkaloid found in cacao beans, and is named after the cacao plant's scientific name. It's toxic to all canids and for a rule of thumb, most domestic animals. Another rule of thumb is that the darker the chocolate, the more theobromine it contains.
The compound is actually toxic to humans, too, but we metabolize it much more efficiently, and so it has less time to accumulate.
You'd find around 60 milligrams of this stuff per 28 grams (1 Oz) of milk chocolate, and around three to four times as much in dark or bakers chocolate. For the average-weight human, it would take anywhere from 0.8 to 1.5 grams for toxicity to become a problem, which would be accompanied by sweating, trembling and a very bad headache. (And a higher risk of a heart attack.)
In accordance with veterinary guidelines, 1.3 grams of dark chocolate per kilogram of a dog's body weight is sufficient to be toxic. Assuming the average human weight of about 77 kilograms, and adjusting the BMI index to account for keidran being digigrade (walking on their toes) and thus being slightly taller, we can guess the average, healthy weight of a keidran to be in the ballpark of 80 or so kilograms. Which just so happens to be the approximate weight of our guy up top!
Knowing this, we can guess that it would take around 104 grams of bakers cacao to be toxic. Some simple math tells us that this is around 130 milligrams of theobromine. Being optimistic about some human traits of metabolism get carried over, we can make an educated guess that we need to have less than a fifth of this dose, or 26 milligrams or less, of theobromine per acceptable serving (how much a keidran could reasonably eat in one sitting) to be considered safe.
Knowing all of this, can we artificially create or genetically engineer cacao or a very accurate substitute to be safe for keidran consumption?
By artificially, I refer to extracting the theobromine from cacao without significantly changing its flavor, texture, etc and being economical to do. (Not needing to use billion-dollar molecular printers to manufacture it molecule by molecule.)
Would doing this be impossible? Will Jayden ever get his wish of hot chocolate as a reward for getting home? (Joke questions.)