I prefer to peel the sweet potatoes, cut them in relatively big chunks, then bake them without adding anything, in a closed glass vessel, in a microwave oven.

I prefer to peel the sweet potatoes, cut them in relatively big chunks, then bake them without adding anything, in a closed glass vessel, in a microwave oven. The baking time depends on the oven and on the quantity, but for example in my 1000 W oven, baking 3 big sweet potatoes needs about 8 minutes. Once you have made a successful test, this method is very fast and perfectly reproducible. Because there is no added water and a part of the water from the sweet potatoes evaporates (but not too much, due to the closed glass vessel), the taste of the sweet potatoes cooked in this way is very intense.