It's definitely possible, but it would take some focus to get it to work. Now, with that said, Beware!: This is something that a person is going to be digesting on DMT. There's a reason why most people prefer to do these substances in a solution (like ayahuasca), and not a sugary chocolate mass. Therefore, this certainly is not for everybody. I would never advise passing these things around to those who are unfamiliar with hyperspace, either, because if done properly the same rules of mind set, setting, making sure the users haven't been taking SSRI's, MDMA, (etc.!) and sacred spaces apply, regardless of the fact the sacrament is just a "Deemster Brownie." :d
Get a box of the best brownies you can find. Organic? Hell yeah! How many brownies does it make? For the sake of space, you might want to double this number, meaning make them smaller. Think about your vomit and digestion for a second. The smaller the better, right?
For every potential brownie in the mix, you want to add ~150mg of extracted harmala alkaloids. The cleaner the better. You need to maintain this number at the end when you go to cut them up, and mix it very well before baking, this way you get as accurate a dose as possible. You don't want to add too much, and you probably don't want to eat more than one of these things! The chocolate alone is going to have a potentiation effect on the harmalas and DMT, and it might even be too stimulating for some people to endure. If you are sensitive to stimulants and harmalas you probably don't even want to consider this. It will definitely be noticeable.
As for the DMT, you want to add that after these are cooked. The harmalas, at least to best of my knowledge, will be unphased by the baking, but DMT wouldn't last.
Maybe try dissolving 100mg DMT (or whatever dose you prefer) per ~15ml of maple syrup or something. Doesn't dissolve? Add a bit of warm butter or something. Mix it with melted chocolate or chocolate syrup so that it can harden at colder temperatures, meaning it will stick to the brownie when cool, instead of just soak it and drip off of it. Make each dose individually in a shot glass or something in the fridge and heat them up just enough when they are cool to disperse on top of the cut up individual brownies that have been cooled as well. Or you could cut out a little hole on the top and drip it in and cool so that it's in the center.
As you can see, it can be done. I wouldn't do it. How will they taste? How will they feel inside of you, and will they work properly in conjunction with a brownie? You are venturing into the sugary world of unknown treats, and will have to answer these questions on your own. Enjoy.