I have now made my second Mock Danish.
This time I used Mascarpone Cheese and I also dissolved the Saccharin-Tablet in water beforehand.

It tasted much better, not sure about the consistency though. It was rising like mad in the microwave, but fell into itself when I took it out, which gave it a "melted rubber"-like look and consistency. Is my Microwave too strong ? Should I use a lower setting ( I nuked it at 700W).

The Saccharin has a nasty aftertaste ( not bitter, just very sweet), but it is the only non-aspartame thing I can find.

My mom will send some german liquid sweetener over. That may be better.