For Brownies
1. Preheat oven to 325 degrees.
2. Mix the brownies per package directions, using the fudgy version if there is a choice.
3. Line two baking sheets with parchment paper. 
4. Spread the brownie mix on one of the prepared pans, spreading until the mix is about 1/2 inch thick. It should nearly cover a normal sheet pan.
5. Bake the brownies for 14-16 minutes, until top is set and center is still a bit gooey.
6. Let brownies cool for about 10-15 minutes until warm but not hot.

For Rice Krispie Treats
1. In a medium sauce pan, melt butter. 
2. When melted, add salt, vanilla and marshmallows.
3. Stir over medium heat until marshmallows are just melted. Remove from heat immediately.
4. Stir in rice cereal until combined.
5. Using a spatula coated with nonstick spray or butter, spread the Rice Krispie Treats on the sheet pan lined with parchment, filling the pan completely. It will be about 1/2 inch thick. 

To Assemble the Pinwheels
1. When brownie is warm and pliable but not hot, cut the brownie in half down the middle of the sheet pan, the short way, cutting through the parchment as well.
2. Cut the Rice Krispie Treats the same way, cutting all the way through the parchment paper.
3. Carefully put one of the brownie sheets (half the sheet pan) on the counter with the parchment side on the bottom.
4. Pick up one of the half sheets of Rice Krispie Treat and place it on top of the brownie with the parchment on top. 
5. Flip the layers so that brownie is on top (see photos in post) and peel the parchment off the brownie layer. 
6. Carefully roll up starting with the longest side toward you.
7. Use your hands to close any holes in the Rice Krispie Treat and to mold the roll to keep the log a round shape. Repeat with the second half.
8. When finished, let cool until brownie is no longer warm.
9. Using a serrated knife, cut the log into 1/2 inch to 3/4 inch slices to create your pinwheels. 
10. Store in airtight container for up to 3 days.