Our oldest cat (Persian, about 13 years) developed a pretty nasty allergy to almost all foods. So she's given enzymatically hydrolysed cat food. If she eats anything else, she'll quickly get diarrhea (usually the next day) and the skin around her face starts itching badly. If she continues to eat the wrong food, she'll start scratching her eyes and ears until they'll start bleeding. Also she'll start coughing badly.
We've taken her to the vet numerous times and they suggested to either treat her with cortisone/steroids until the end of her days /which works well, but then she's hungry all day and therefore stressed out) or use enzymatically hydrolysed wet cat food. The food actually works pretty well, if she's eating it. However she really doesn't like it and only nibbles on it. Usually she gets 3 portions a day of 45 to 50 g each (1.6 to 1.75 oz). Yesterday she didn't even finish one of her servings.
I can understand her: the texture is like pudding and it's pretty sticky. Also it smells bad. I wouldn't want to eat it, either. Unfortunately it's the only food we have that she can digest without facing the issues mentioned above.
What we've tried
We also got a bag of enzymatically hydrolysed dry food, since she loves to run after pellets thrown across our apartment. Unfortunately even a small serving leads to diarrhea almost immediately (upon the next litter box session).
Mixing it with water
We mixed and mashed it with water. This changes the texture of the food. It worked for a few days, but she eventually figured it out and now refuses to eat this.
Mixing it with other hypoallergenic food
I've mixed the hydrolysed food with some other hypoallergenic food (she got that before) at the ratio of 8:1. Unfortunately there was diarrhea in the litter box afterwards.
Mixing it with malt paste
While she likes malt paste per se and she won't show any of the symptoms because of it, mixing it with the food didn't make her eat that, unfortunately.
What else can we do to make that food palatable to her, without introducing the problems mentioned above?