Preheat the oven to 350 degrees. Grease a 9 x 13 x 2-inch baking pan.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar on medium speed until light yellow, about 2 minutes. With the mixer on low speed, add the vanilla, eggs, and peanut butter and mix until well combined.
In a small bowl, sift together the flour, baking powder, and salt. With the mixer on low speed, slowly add the flour mixture to the peanut butter mixture. Mix just until combined.
Spread two thirds of the dough in the prepared pan, using a knife to spread it evenly. Spread the jam evenly over the dough. Drop small globs of the remaining dough evenly over the jam. Don’t worry if all the jam isn’t covered; the dough will spread when it bakes. Sprinkle with the chopped peanuts and bake for 45 minutes, until golden brown. Cool and cut into small squares.
Copyright 2006, Barefoot Contessa at Home by Ina Garten, Clarkson Potter/Publishers, All Rights Reserved