Place dark chocolate chips, 3/4 cup peanut butter, and 4 tablespoons butter in a microwave-safe bowl. Microwave on high until melted and smooth, stirring every 30 seconds (total duration approx. 90 seconds), then stir in kosher salt.

Add the rice cereal to a large bowl and pour the melted chocolate mixture over it. Fold until cereal is evenly coated, let rest for 15 minutes.

Add 1 cup powdered sugar to the cereal mixture, fold until evenly coated. Spread it into an even layer on a parchment-paper-lined baking sheet. Set aside.

Melt marshmallows with remaining 4 tablespoons butter in a bowl (approx. 45 seconds), add the 2 tablespoons peanut butter, microwave for 30 seconds more until smooth.

Fold marshmallow mixture with the prepared chocolate-coated cereal thoroughly until combined.

Spread into a greased pan, let cool and set at room temperature for 1 hour.