Line an 8x8-inch baking pan with parchment paper and set aside. Tip: Use the greasy side of the butter wrapper from the butter to grease the pan before putting the parchment in to help it stick and stay in place.
Add the 3 cups powdered sugar to a large mixing bowl and set aside.
3 cups powdered sugar
In a medium-sized saucepan over medium heat, melt the ½ cup unsalted butter. Then stir in the 2 cups light brown sugar and 5 ounces half & half and bring it to a boil. Once boiling, allow to sit untouched for 1 minute and 45 seconds.
½ cup unsalted butter, 2 cups light brown sugar, 5 ounces half & half
Remove from heat, then stir in the 1 cup creamy peanut butter and 2 teaspoons vanilla extract until smooth and creamy.
1 cup creamy peanut butter, 2 teaspoons vanilla extract
Pour the hot peanut butter mixture into the bowl with the powdered sugar, then beat with an electric mixture until completely smooth.
Pour into the prepared pan and spread it out quickly with a rubber spatula. Let sit until completely cooled and set.