WARNING: Do not try this at home. I can't picture a scenario in which this information will be useful to anyone, excepting that small crowd which has no oven, a propane stove, and an eight-quart pressure cooker. Small crowd, this post is for you.
Just for the record, I started out baking something slightly more essential (and successful) - bread. You can read about it here, and you can rest assured that this has been the recipe for bread that we've followed ever since we found it to be successful.
My first endeavor was brownies. I used a mix (half the box) to make things really simple. I mean, who could screw up brownies from a mix, right? Wrong. Apparently eggs are not an optional ingredient. I tried to compensate for lack of eggs by adding either extra oil or extra water, I don't remember which. Either way, the brownies never really baked, they were a sort of thick goop.
The next batch, we had some farmer's market eggs (fresh eggs - we didn't refrigerate them for a week and they never got rotten). So I used the other half of the first box and tried to use minimal amounts of liquids. I baked them on the smallest burner on the lowest setting - our stove is hot - and I had the lid on the pressure cooker but I did not cook them under pressure. I had them in for maybe 30 minutes and they smelled burnt. It turns out, they burnt (the propane stove is very hot). Also inedible. Nearly ruined the pressure cooker, which is our main cooking pot when it comes to making meals. Lesson learned: better to be underdone than overdone. Here's the pressure cooker soaking - the engine was running and the vibrations showed in the water.
It seems to be a theme - two or three trial runs before a success. So a couple weeks later, when my sweet tooth started getting to me again, I tried cookies (also from a mix; I have all the ingredients to make them from scratch, but a mix is more reproducible). I used powdered egg mix this time instead of real eggs. I could only fit six in the pressure cooker, and I had them on the bigger burner at the lowest setting. I baked them for about 10 minutes and they turned out a little soft on top (so they collapsed) but they were still pretty good.
The next round I put them in for about 12 minutes and as you can see it was a little too much time. They were pretty inedible. Kyle and I picked off all the non-burnt parts and ate them immediately. This batch was a failure, so after this I moved the cooker to the smaller burner.
After that, I decided there was no way I'd be able to make cookies like I could in the oven. When I burnt them, the tops were still soft, so it didn't look like there was any way I could cook them through. The next time I made cookies, I "baked" them all on the small burner and lowest heat for 8 to 10 minutes, and even though it doesn't look that appetizing, I consider it a success. They were still delicious, although Kyle implied they were better suited to being crumbled on top of ice cream, I think ice cream is the one favorite food that I just can't have on the boat.