I'm making brownies for the first time, so I went with cake-like but everyone wants chewy. I agreed but realized it was too late. They're already in the oven, how do I fix it to chewy?
Take a look at this video for mode details, but what makes a diference between fudgy&chewy to a cakey is the fat ratio.
Since the brownies are already in the oven it is likely too late to increase the amount of butter in the brownie batter. Your best bet is to add a metal baking sheet at the bottom of the oven and add about a cup of water. The goal would be to have steam rise from the baking sheet add some moisture to the brownie. While this is no substitute for more butter in your brownie batter it will lend itself to a more chewy texture. You may also want to bake the brownies for slightly less than you would normally do so.
If the brownies are already cooked and out of the oven at room temperature, you could try steaming them in manner similar to the way restaurants steam already cooked bread to give it a warm and soft texture right before serving to guests.