I made these. Yowza! Will be making them often! A couple notes...
I caved and bought a box brownie mix for this. I usually buy the Ghiradelli brand but tried to save a buck and bought the Duncan Hines. Never again.
The recipe is written for a 9x13 pan, but because of the brownie mix, I used an 8x8 pan. I divided all the other ingredients by half...and it worked like a charm! (And was plenty. They're on the rich side so I cut them in roughly 1" squares. I had plenty for folks at the office, my morning barista crew, and some for home.)
For an 8x8 pan, the recipe calls for 1/2 cup of chopped peanut butter cups. FYI, that's 2 "candy bar" sized packages of Reeses. Next time I'll use 3. (When you cut the brownies, you really didn't see much of the peanut butter cups, I want to bump that up.)
Also, for the 2nd layer with peanuts and chopped peanutbutter cups, the recipe has you sprinkle them over the hot brownies, and then toss the pan back into the oven. I'm not really sure what the point of that is. You want to see the chunks. The chunks don't melt well anyway. And then you pour the hot chocolate/peanut butter/rice crispy mixture over the top. Long story short? I wouldn't bother with the 2nd trip in the oven.
I was worried about the consistency of the brownie base vs. the chocolate (thinking I'd try the recipe the way it was written, but anticipated adding an extra egg to the brownie mix to firm it up the next time I make them--totally not necessary), it worked out great!
I'd say the biggest advantage to making this version vs. the one I posted earlier...no need to chill between the various layers. Also, unlike the other recipe, this one, I like the consistency both chilled and at room temp. Conclusion? I like both recipes but I have a feeling I'll make this one more often.