The challenge with “meatballs” containing spinach and sweet potato is most definitely the moisture. Squeezing the wilted spinach well is obviously required. But the potato is trickier. Leaving the mashed up potato in the fridge for a period helped, however even after 45 minutes the mixture was distinctly soggy. If you’re truly invested then perhaps suspending it overnight in muslin or a sieve would do the job… But I question the worth. The addition of breadcrumbs to the mix to dry things out a little was likely required and it’s quite possible that adding more of them than suggested in the recipe would help further.
45 minutes resting worked just about enough, albeit with the balls becoming a little flattened in the oven.
The crisped up panko coating worked wonderfully, contrasting with the squish of the middle. These were a pleasurable thing to munch upon. You could probably play with the flavours quite a lot too, it’s quite a robust thing.
I added far more cheese than was suggested and I don’t see why you wouldn’t. The paltry quantity in the recipe is parsimonious to the extreme.
A worthwhile warning for future reference is that these balls are by no means quick. Between preparation, resting and not inconsiderable oven time we got mighty hungry. Not necessarily week night fayre.
From The Bowler’s Meatball Cookbook, pg. 82