I baked macarons earlier and this happened. You can see that they're pretty tall (which I don't want) but mostly importantly, what happened to the shell? I baked at 290F for about 20 minutes (they're about 1.5 inches). I can't tell whether the middle is underdone or whether the ridges are well done. It seems that interior is most full in the center.
I'm thinking I might not have deflated this properly during macaronage and it needs to be cooked at a lower temperature.
Edit 1: I used a new recipe via Chef Nini and it solved them problems I was having. This time, I paid close attention to the temperature of the oven and overbaked them a little. I'll let the maturing to take care of softening them again. I made chocolate shells and most turned out well. The ones that were piped last were a little overmixed in the bag and turned out a little funky (top collapsed, wrinkled). I'll wait around to vote for best answer though.
Edit 2: Some of them still collapsed in the middle, but it's by an acceptable amount. However, some are still a little hollow, which is disappointing. Onto more trials!