Grease or line a 8x8x3” baking dish with wax paper.
In a large pot over medium-low heat, melt the butter and marshmallows, stirring often with a silicone spatula. When the marshmallows have melted, stir in the peanut butter and turn off the heat.
Fold in the Rice Krispies until thoroughly combined, then press half the mixture into the greased/lined pan. (It’s okay if it’s not completely level at this step; the jam layer will be rippled and wavy, which looks kind of cool.)
Spread the warmed preserves on top, making sure to get all the way to the edges.Press on the remaining Rice Krispies mix on top, getting it as level as possible.
Cool for 45 minutes, then cut into squares or bars. These are best if eaten within a day or two, but they can be stored in an airtight container for up to three days.