By far the one with the red peppers was my favorite. Oh my gosh, was it ever awesome. I sauteed the peppers a bit so they were a bit softer, and caramelizing onions was totally easy. You basically pour some olive oil in a skillet, slice up an onion (or however many you need), then stir about every five minutes for 20 minutes, adding more oil if needed. One regular sized onion yielded roughly 2/3 cup caramelized onions.
The shittake mushroom one was good, too. The original recipe called for button mushrooms and red onions as well, but I didn't do those. I had John try some gorgonzola cheese before I put it on to see what he thought, figuring if he wasn't a big fan I'd just do a little, but he really liked it so we put quite a bit on. I also put some mozzarella on both of those. I wasn't sure how it was going to be with the sour cream as the sauce, but it totally worked. I was thinking some kind of spreadable cheese like Boursin would be good as a base, too.
Both were excellent combinations of toppings.