Heat oven and prepare brownie batter according to package directions. Fold semi-sweet chocolate morsels into brownie batter. Spread in a 9x13 pan lightly coated with cooking spray.
On top of brownie batter, lightly lay a single layer of mini pretzels. I had 6 rows, but this may vary depending on the size and brand of your mini pretzels.
Bake according to brownie package directions for a 9x13 pan, plus 2-3 minutes. Use the toothpick test to determine if the brownies are fully cooked.
Remove brownies and change oven temperature to high broil. Top pretzel brownies with marshmallows and return to the center of the oven. Watch very closely until marshmallows begin to blistery, bubble and melt. When they reach your desired level of char, remove. Allow to cool slightly before cutting and serving. Enjoy!
If you've tried this recipe, come back and let us know how it was!