Re Rommertopf (Clay Pot)

Arthur, click the search button at the top of your screen and enter "clay pot." You'll find lots of useful info. Here is a repost of basic instructions I contributed here a couple of years ago:
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here are the basics of using a clay pot (Rommertopf):

Soak both the lid and bottom for 15 minutes in water - it's meant to be used WET. I put a big clean plastic laundry tub in the bathtub so lid and base can be submerged together and not occupy my sink. Do not dry, but shake off any dripping water before carrying to kitchen ;-)

Use it only in the oven, never on a stove top. Food is usually cooked in a hot oven with clay cookers (400F or more). The "rule of thumb" is to add 100 degrees F and about 30 minutes cooking time when converting recipes for a clay cooker (poultry, though, usually takes less time than conventional roasting). Food is cooked covered for most if not all of its baking time. (This has the added advantage of keeping your oven clean - no splatters!) Even though it's covered, things generally brown beautifully and do not have to be browned separately before roasting in the clay cooker. Another very important point, do NOT preheat the oven. Clay is fragile and doesn't like to change temperature rapidly. So you start with a cold oven and let the oven and the pot warm up gradually together. A clay cooker is great in a microwave as well as in your conventional oven.

Let it cool before cleaning and don't put in dishwasher. You can soak it with warm water and just a few drops of liquid soap or soak with baking soda (which will also help get rid of any pungent food odors). You can line it with parchment paper before adding food - it isn't necessary but it's a good idea if you're going to do strong flavors, perhaps with lots of garlic - clay is porous and you don't want those flavors retained so that tonight's poached pears taste like yesterday's garlicky spareribs...

If the one you purchased had never been used, or you can't tell for sure, treat it like a brand new one and soak both top and bottom, completely covered with water, for half an hour, then scrub well with a brush to remove any clay dust. After that first long soaking, you will only need to soak 15 min each time you want to cook in it.

Enjoy it - it's a wonderful way to cook! And there are lots of cookbooks and I'm sure a gazillion recipes here at TKL for it. I especially love to bake bread in it.