Preheat oven to 350ºF and line an 8x8" baking dish with parchment paper.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, peanut butter, and brown sugar together until smooth, about 30 seconds. Add the eggs, one at a time, beating well after each addition. Mix in the vanilla. Add the flour and baking powder and stir until just combined, don't overmix.

Press 2/3 of the batter into the prepared pan, smoothing out the top. Spoon dollops of the fluff evenly over the batter. Follow this up with dollops of the jam/jelly. Top with remaining batter by taking spoonfuls and flattening slightly, then placing them evenly over the fluff/jam layer. It's ok if some of the fluff or jam is peeking through. Sprinkle the peanuts on top.

Bake for 25 to 28 minutes, or until the top is no longer glossy and the edges are golden brown. Immediately sprinkle the peanut butter chips over the top. Cool completely before slicing.

Blondies will keep airtight at room temperature for up to 1 week, or in the freezer for up to 6 months.