Set a rack to the center of the oven and preheat to 325℉. Lightly oil a 8×8 metal cake pan and line with parchment paper, leaving enough to overhang two sides of the pan to act as handles to remove the baked blondies from the pan.
To make the blondies, melt the butter in a large microwave-safe bowl.
Add the brown erythritol and allulose and mix well.
Add the eggs to the butter mixture and beat until well blended.
Mix in the pure vanilla, then add the Peanut Butter Keto Chow and mix until it is fully absorbed. The batter will be thick.
Stir in the crushed peanuts.
Spread the batter evenly into the prepared pan.
Bake for about 20 minutes, or until the edges begin to brown and the center is lightly set.
Let the blondies cool completely before frosting.
To make the frosting, beat the butter in a large bowl with an electric mixer.
Sprinkle the powdered erythritol over the surface of the butter and blend on low speed until it is all absorbed, then raise the speed to medium and beat until light and fluffy.
Add the Grape Keto Chow and beat on low until well combined.
Add the heavy cream and beat on medium speed until the frosting is a spreadable texture. It will be very thick but should be creamy and smooth.
Spread the frosting over the cooled blondies.
Cut the blondies into 20 small pieces.
Store leftover blondies in a single layer, in an airtight container in the refrigerator for up to a week, or in the freezer for up to three months.