Making Egg Flan

On thursday,in our class we made Egg Flan in our science class.
it tasted like pudding,but caramel is tasted bitter.
The ingredients is:
1.10 egg yolk
2.condensed milk
3.one cup of fresh milk
4. four table spoon of sugar
We made this cake to learn about compound and mixtures.
First we add egg yolk and mix it with hand mixer,then we add fresh milk and condensed milk,after that we make caramel from sugar and then,we mix it with the egg yolk mixture with the caramel. Then we steam it ,we wait for about 1 hour. After that we tasted the Egg Flan it was dilicius but it was bitter and also soft.