2 cups all-purpose flour
1/2 tsp baking soda
1/4 tsp salt
3/4 cup unsalted butter
3/4 cup smooth peanut butter
1/2 cup granulated sugar
1/2 cup packed light brown sugar
1 tsp vanilla
In a bowl, combine flour, baking soda, and salt. Set aside.
Cream butter, peanut butter, and sugars at medium-high speed of an electric mixer, until light and fluffy. Stop to scrape down the sides as need be. Add the egg and vanilla, then switch to a slower speed, and add the flour mixture, again, stopping to scrape down the batter when needed.
Halve the dough, and shape into disks. Wrap in plastic wrap and refrigerate for at least 45 minutes.
Preheat the oven to 350 degrees. On a lightly floured surface, roll out the dough to about 1/4 inch thick. Cut the dough into 2 1/2 x 1 inch rectangles.
Transfer the cookies to baking sheets lined with parchment paper, placing them about an inch apart. Score the top of each cookie with the tines of a fork. Refrigerate for 15 minutes. Bake for 15 – 20 minutes, or until the edges are just slightly more golden than the rest of the cookie. Let cool on the sheets for at least 10 minutes before transferring to wire racks.