The first recipe I tried was the Peanut Butter Swirl Brownies from Brownies and Broomsticks by Bailey Cates (my review is here). The brownies are mentioned several times in the book, most frequently referred to as Katie's favourite treat. The following passage was so mouthwatering I needed to bake these:
"I needed to digest the conversation with my parents and figured I might as well digest some comfort food, too. The salad had been healthy to an almost holy degree, and now it was time for some sweet goodness. First I stirred up some simple brownies using the old trick of adding boiling water to the batter to make them extra moist. Then came the best part: chunky peanut butter mixed with soft butter, confectioners' sugar and vanilla and dolloped on top of the brownie batter. I drew a knife through the combination to create a chunky marbled effect and popped the pan into a hot oven." ~ pages 125-6
These were really fun to make, especially as my two-year-old niece helped :) The recipe is clear and easy to follow, with all the measurements in US cups and tablespoons. With my niece's help it took us about 45 minutes to prepare pre-baking (chances are you could easily halve that time if you don't have a toddler erm helping) and then a further 35-40 minutes to bake.
I stuck to the recipe throughout as my go-to brownie recipe doesn't have any water added so I didn't want to mess with things. You could probably convert it from US cups but to be honest it's not too hard to find a set (I have two) and they are a lot easier to use, especially when cooking with kids.
The only part of the recipe I would change is to make the peanut swirl topping after the brownie mix is made and in the pan as it thickened considerably when making it first. I was able to thin it a little by placing the mixing bowl into a larger bowl of hot water (essentially how you melt chocolate), but when you have a toddler anxious to see the results of their cooking you have to work fast so mine went on lumpy.
The final result:
And the taste? I really enjoyed them. The brownie is dense and has a rich, dark chocolate-y taste while the peanut topping adds a hit of sweetness and contrast. They were also approved by my niece who said they were "nom noms" :) The only person who wasn't overkeen was my brother-in-law but he isn't a big fan of peanut butter.
If you aren't a fan of nuts in your brownies, you may not like using crunchy peanut butter for the swirl. Given that the peanut layer puffs up and bakes onto the brownies, you could probably substitute smooth peanut butter with no problems. We don't often have chunky peanut butter at home so chances are I'll try this out at some point.
For people with food intolerances - these are dairy free, but do contain gluten, eggs and nuts.