Preheat the oven to 350 degrees F and line a small baking pan with parchment paper.
Melt the butter and chocolate chips together in a microwave-safe bowl, stirring until smooth.
Stir in the sugar, egg, and vanilla extract until fully combined.
Add the flour and salt, then mix until just blended.
Fold in 2 tablespoons of the peanut butter to create swirls in the batter.
Pour the batter into the prepared pan and bake for 20 to 22 minutes until a toothpick comes out with a few moist crumbs.
Let the brownies cool completely in the pan.
Warm the remaining 2 tablespoons of peanut butter and dot small amounts on top of the cooled brownies.
Press 3 candy eyeballs onto each brownie using the warm peanut butter to help them stick.