Begin by lining an 8x8 inch square baking pan with parchment paper or spray with nonstick cooking spray.

In a large pot set over medium-low heat, melt the salted butter. Stir in mini marshmallows, creamy peanut butter, and sea salt until smooth.

Remove pot from heat and fold in Rice Krispies cereal. Add vanilla extract and remaining mini marshmallows.

Press half of the mixture into the bottom of the prepared pan, then layer the whole Reese's cups on top.

Spread the remaining Rice Krispies mixture over the Reese's cups, pressing gently.

Sprinkle chopped Reese's peanut butter cups on top of the final layer.

Combine chocolate chips, creamy peanut butter, and a little salted butter in a microwave-safe bowl and microwave until melted.

Drizzle the melted chocolate mixture over the top and refrigerate for at least 30 minutes until set. Cut into squares to serve.