Matzo balls (made in good chicken stock) are magic for this sort of thing. Nutritious, filling, and when eaten warm, super-soothing to sore mouths/ throats.
(My daughter had a bunch of ear/nose/throat surgeries at the same time and when she was recovering, matzo balls really got her through.)
Edit: here's a post I made at the time.
Meanwhile, if anyone comes across this via Google in the future, this is what worked well for us:
The big star was/is overcooked, mooshy (NOT al dente) macaroni and cheese, with a little extra milk. This was the first thing she ate in any quantity, and it's still what I give her if she's a little sore.
Overcooked pasta with Alfredo sauce offered a variation on a theme.
She also had a lot of scrambled eggs early on.
Soft (slightly melted) vanilla ice cream was one of the first things she could eat/drink/ingest.
Jello was very, very useful for getting fluids into her when she had a really hard time drinking. When I felt she hadn't had enough fluids I'd set her up with a book or a computer game (something distracting) and then just spoon a bowl's worth into her, using a small spoon.
Strawberry syrup -- the kind sold next to chocolate syrup -- used to make strawberry-flavored milk worked well a bit later in her recovery.
Smoothies did NOT work for her, and I never figured out why. The first was made with a bit of mango and I thought that might be the problem. (Other ingredients -- banana, yogurt, milk.) The next had no mango but still made her throat hurt -- I thought it might be from using the straw, having to work a bit to ingest. The third had no mango and I gave her a spoon, not a straw -- still hurt her throat after a few spoonfuls. She had a banana without much problem, so maybe the yogurt was the issue? Dunno.
Also, any kind of hard popsicles were a bust. Like those fancy chamomile tea ones I made -- didn't work. The only ones she liked were smooth/ creamy and soft.
Chicken soup with matzo balls was tried a bit too early I think but it was one of the first food-food (as opposed to dessert) items she could tolerate.
Pudding! Wonderful stuff. Second only to jello. Chocolate, vanilla, tapioca.
Very ripe avocado was a good way to get some veggies/ healthy stuff into her.
Mashed sweet potatoes were another way.
Tried lots of other things -- some successes, some failures -- but those were the main things that a) were really useful or b) were a surprise failure.
The rest of the thread has some good tips, too: