Dissolve junket in dab of room temp water and set aside.
Mix sugar, flour and salt very well, dry.
In big stock pot, beat eggs.
Add half-and-half.
Slowly mix in sugar mixture as you heat and stir.
Heat until too hot to touch but not at boil.
Let it cool to temp of bath water, then add dissolved junket.
Stir quickly, and then let sit quietly for a couple of hours at room temp.
Sit in fridge until ready to freeze.
Add vanilla. (Optionally add lemon for jelly)
Pour into freezer and crank until frozen.
(Add jelly when almost frozen and crank a bit more.)