I think I need a couple more tries before I can be sure. I've had similar problems. I used to try to make fries with them. Does not work.
Right now I cut them into maybe 2cm cubes, put them in a bowl with oil and toss them until they are lightly covered. Put them on the pan then season them on the pan.
The thing I noticed with doing sweet potatoes in the oven is there's like this small 2 min period between them being undercooked and burnt to a crisp. I still tend to overcook ![]()
If I figure it out I'll let you know
