Good morning. I understand. I can tell you how much if I knew the amount of flour your recipe contains. Take the weight of the flour & multiply that by 2.25% & that will give you a fair amount of fresh yeast to employ.
15, oz of flour X 2.25%= .334%. That equates to 1/3rd of an oz. In the supermarkets the small little cakes of fresh yeast are 5/8ths of an oz. (.625) Just use 2 of them.
Candace, I hope I was helpful to you. Remember young lady, If you require more assistance please post the recipe & directions & how you will be baking these yeasted lean bread buns. I then can be more helpful to you.
Good luck & enjoy the rest of the day.