Line an 8x8-inch baking pan with parchment paper, leaving some overhang for easy lifting later.
In a microwave-safe bowl, combine chocolate chips and coconut oil. Microwave in 30-second bursts, stirring between each, until fully melted and smooth.
Pour half of the melted chocolate into the prepared pan and smooth it out evenly. Pop it in the freezer for about 10 minutes to set slightly.
Meanwhile, in a separate bowl, mix together the peanut butter, melted butter, and vanilla extract until smooth. Gradually stir in the powdered sugar until fully combined and creamy.
Spread the peanut butter mixture over the chilled chocolate layer, smoothing it out evenly.
Pour the remaining melted chocolate on top, spreading it to cover the peanut butter layer completely.
Refrigerate the fudge for at least 2 hours, or until fully set.
Once set, lift the fudge out of the pan using the parchment overhang. Slice into squares and enjoy!