how to make health bar hold (stick) together
I would advise omitting the cream, as you mentioned yourself. It's a liquid, and combined with the ground sunflower seeds, eggs, butter, honey, and vanilla in the bottom of the pan, chances are good that that was your "cake." If things seem too dry as you mix them together, I would suggest adding another egg—it will help stick things together and add moisture without being as likely to stay moist, which is probably what created the cake texture. Eggs solidify with heat, they don't just evaporate like milk or cream.