Line a mini muffin tin with 24 paper liners.
Microwave 1 cup chips at 30-second intervals, stirring until smooth.
Spoon about 1 teaspoon chocolate into each liner to cover bottom; refrigerate 10 minutes.
Meanwhile, mix peanut butter, powdered sugar, butter, vanilla, and salt until smooth and combined.
Roll filling into 24 balls; flatten slightly and place on chocolate bases.
Melt remaining chips; spoon over filling to cover completely.
Refrigerate at least 30 minutes until set; keep refrigerated up to 2 weeks or freeze up to 3 months.