great thread!
I frequently have a hard time cooking halibut to the proper doneness. It seems there is a razor-thin margin between nicely cooked and tough and overcooked.
Homemade pasta and I are not friends- I think I always overwork it, and it has the texture of a rubber band.
Lentils are also a thorn in my side. Too often I wind up with a lot of unabsorbed liquid and a pot full of mush.
I usually do ok with risotto, but it is such a pain in the butt that I've all but abandoned it in favor of paella, which is almost impossible to screw up and really easy to make.