Heat oven to 350*F. Butter 9 x 13 pan with butter, then line with parchment paper. Butter parchment and dust with flour. Mix together butter and sugar in mixer, until fluffy (2 minutes). Add eggs and peanutbutter, about 2 minutes. Combine dry ingredients, and add until combined. Add vanilla. Take 2/3 of the mixture and line the 9 x 13 pan. Spread jam on top of the mixture. Crumble remaining peanutbutter mixture over the jam, along with shopped peanuts. Bake 45-60 minutes (tent with foil if they're browning too quickly). Allow them to cool, then refrigerate for 1-2 hours. Cut into 36 pieces, serve at room temperature.