Line a 9x9-inch baking pan with parchment paper or use a nonstick pan.
Pour 2 cups chocolate chips into a microwave-safe bowl. Melt on high in the microwave in 30-second increments, stirring between each until smooth.
Spread chocolate in bottom of the prepared pan.
In a medium-size mixing bowl, use a hand mixer to beat together 1 1/2 cups peanut butter with 1/2 cup powdered sugar. Spread over the chocolate which should be mostly hardened.
Pour the remaining 2 cups chocolate chips into a clean and dry microwave-safe bowl. Melt on high in the microwave in 30-second increments, stirring between each until smooth.
Spread on top of peanut butter layer. Let harden completely before cutting.