Hilchos Shabbos #5- Laws of Chazara

I enjoy sampling the cholent on a long winter Friday night.  What is the procedure for removing some and returning the pot  to the fire? How can I save a cholent that is drying out? Can I remove a kettle from the blech to make a cup of tea on Shabbos, and then return the kettle to the blech to remain hot. If the electricity went off on Shabbos and was subsequently restored a few hours later by non-Jewish workers, what is the status of the reheated food, such as cholent?