Spray sides of a 9-inch tart pan with cooking spray and line bottom with parchment. Set aside.
In a medium bowl, beat peanut butter and butter with an electric mixer until smooth and creamy.
Add powdered sugar and salt.
Stir until combined. Set aside.
Combine chocolate and oil in a large microwave-safe bowl.
Heat in 15 second increments, stirring after each until melted and smooth.
Pour half of chocolate into prepared tart pan.
Freeze until set.
While chocolate is freezing, scrape peanut butter onto a piece of parchment paper.
Roll, or pat, into a 8½-inch circle.
Transfer, still on the parchment, to a sheet pan.
Freeze until set.
Once chocolate and peanut butter are both frozen, remove from freezer.
Place frozen peanut butter disc on top of frozen chocolate.
Pour remaining chocolate over top.
Freeze until set.