Cook till they are tender! That's how long! Squeeze them soft then they are done!
But here's a Cuban version of that, very thing, and they are Super too!
Instead of regular Sweet Potatoes buy the fresh Yams, they look the same, so ask them!
Then you peel them and slice in round pieces about 3/8 of an inch thick!
Then put them in a bowl and cover with water and put it in the Frig for 24 hours.
Drain and rinse very good! (You've removed a lot of the tar they have)
Now fry in Virgin Olive Oil! They should be still tender when they are done!
Cubans serve this with Fresh Baked Pork and Black Beans with White Rice!
When the beans are 90% cooked add two spoons of white Vinegar!
This is one of the National Dishes of Cuba!