How do I get the right amount of heat from Carolina Reapers in cookies/brownies?
Easy! You'll need to first make "Carolina Reaper powder"


Dry them by running a fishing line or thread near the stem and hang
them in a dry place for 3 days.
Once they are dry, remove the stems and place in a spice grinder or food processor.
Place the powder in a spice container.


One you have made your Carolina Reaper powder, you can proceed to make your brownies as normal, and add a pinch to the batter. The Scolville Units of your peppers will vary based on your plants vs someone else's, so it's difficult to recommend a precise amount of powder to use. That will also depend on how spicy you want these devil brownies to be!

To calibrate the right level of spiciness, this jalapeno brownie recipe offers a good baseline. Based on some rough math, the recipe calls for 1 Million Scolville units. A single Carolina Reaper contains roughly 1.6 Million Scolville units. So you could use about 2/3 of one whole pepper, or you could use the amount of powder you get from 2/3 of a pepper.

EDIT: Based on some rough math below, approximately .04 dried peppers would be needed to accomplish the level of heat in the recipe above.