Hi, I have a problem with Joule Creme Brulee recipe. I was cooking it in 83 degrees Celsius for an hour. Recipe exactly from the app. I got a grainy consistency:

After stirring it in the jar - it came much more smooth and silky:
Why it is so grainy after cooking? What I can do to get silky and creamy consistency in the jar (just like in the Joule app)?