Cooked or raw mushrooms on pizza?

Short answer: It Depends.

Long Answer:

You are correct that the decision on precooking mushrooms before putting them on pizza is about controlling moisture. For some hefty mushrooms like portabellos, it's also about making sure that they cook fully. Here's what to factor in:

• What's the density of mushrooms per pizza area? That is, how much space between slices?
• Are these hefty mushrooms (white, crimini, portabello) or delicate mushrooms (chantrelle, oyster, enoki)?
• How thickly are they sliced?
• Are there other "wet" items going on the pizza topping, like a sauce or fresh tomatoes?
• How thick is the crust?
• How long will the pizza cook, and how hot?

On one end of the scale, if you're making a thin-crust pizza with tomato sauce and covering it completely in thickly sliced portabellos, you pretty much certainly should precook them. However, if you're making a deep dish pizza with only a few thin-sliced white mushrooms on top, then don't bother. Stuff in between is up to your judgement.

For pizza restaurants, American Pizza is a medium crust, and they generally don't put that many mushrooms on each slice, so it's fine to put them on raw. However, I've been to thin-crust Neopolitian-style pizza places where they did, indeed, partly cook the "wild mushrooms" ahead.

Also, if you are precooking the mushrooms, you want to cook them in a way that will remove moisture. That means broiling them in the pizza oven on a baking sheet with parchment ... not sauteeing them.

Pizzas are cooked under intense heat, so precooked mushrooms will tend to get overcooked. There's no need to precook them, even if you are adding a lot of them. I would always buy whole mushrooms and slice them myself, pre-sliced ones tend to dry out and they won't taste as fresh.

I thickly slice mushrooms and then pan fry to get them coated with oil and to season (salt, pepper, thyme).

The oil and thick slicing prevents the mushrooms from getting too dry. I've had thinly sliced raw mushrooms on commercials pizzas and don't like the dry almost chewy texture.

I've never had problems with raw mushrooms on pizza turning it soggy. I have always seen them putting raw mushrooms on pizza at the places I go to.

The only reason to sauté them would be to add extra flavor.

If lightly-cooked mushrooms aren't your thing, and you're making pizza on a stone in a domestic oven, it's quite possible they won't cook enough while the pizza cooks. So I pre-cook mine.

I used to microwave them then drain them, and that works, but I've found something better.

Now I just slice them and put them flat on a baking tray in the oven for 2-3 minutes when it's nearly preheated. This leaves them much drier and less prone to making things soggy than microwaving or even frying. I don't use any oil, but you could.

Mushrooms should be pre cooked to remove moisture and placed below the cheese to prevent drying out.