1 cup all-purpose flour
1/4 cup confectioners sugar
1/4 cup creamy peanut butter
1/2 cup unsalted butter, softened
about 2 heaping cups marshmallows (most of one 10-ounce bag; I used large marshmallows, use mini if you prefer bars not as thick)
one 10-ounce bag peanut butter chips
1/3 cup light-colored corn syrup (not 'lite')
2 tablespoons unsalted butter
2 teaspoons vanilla extract
1 1/2 cups Rice Krispies or similar crispy rice cereal
1 1/2 cups salted peanuts or salted honey roasted peanuts
Preheat oven to 350F. Line an 8-by-8-inch baking pan with aluminum foil, spray with cooking spray; set aside.
Crust - In a large bowl, add the flour, confectioners' sugar, peanut butter, and cut in the butter with two forks. Keep working until mixture is combined and pea-sized crumbly bits are present.
Turn mixture out into prepared pan, hard-packing it with your fingertips in an even, smooth, flat layer to form a crust. It's sticky and a bit challenging to work with but just take your time. Bake for about 15 to 17 minutes, or just until set. Don't overbake since pan is going back in to melt marshmallows, or crust will be crumbly.
Middle - Remove pan from oven and evenly sprinkle with marshmallows. Return pan to oven for about 3 to 4 minutes (but start watching closely after 2 minutes) or until mallows are puffed; don't brown them and watch them very closely so they don't burn.
Mini marshmallows will puff quicker and turn brown faster than large ones. Remove pan from oven; set aside.
Topping - In a large microwave-safe bowl (same one used for crust is okay, just wipe with a paper towel), add the peanut butter chips, corn syrup, butter, and heat on high power to melt, about 2 minutes total but stop to check and stir every 30 seconds and heat in short burst until mixture can be stirred smooth.
Add the vanilla and stir to combine.
Add the cereal, peanuts, and stir to combine.
Turn mixture out on top of marshmallows, smoothing the top with a spatula and lightly smooshing it down so the layers meld together.
Cover pan with a sheet of foil and place in the fridge for at least 2 hours, or until set, before slicing and serving. Bars will keep airtight at room temp for up to 5 days, or in the freezer for up to 6 months.