In bowl of electric mixer or by hand, beat butter until creamy. Add sugars; beat until fluffy, about 3 minutes with electric mixer, stopping to scrape down bowl as necessary. Beat in peanut butter until fully incorporated, then eggs, one at a time, then vanilla. Gently stir dry ingredients into peanut butter mixture. Add ground peanuts; stir gently until just incorporated.
Working with 2 tablespoons dough at a time (see illustration 1 below), roll into large balls, placing them 2 inches apart on a parchment-covered cookie sheet. Following illustration 2, press each dough ball with back of dinner fork dipped in cold water to make crisscross design. Bake until cookies are puffed and slightly brown along edges, but not top, 10 to 12 minutes (they will not look fully baked). Cool cookies on cookie sheet until set, about 4 minutes, then transfer to wire rack to cool completely. Cookies will keep, refrigerated in an airtight container, up to 7 days.
Submitted By: Betsy
Original Source: The Best Recipe
Bringing the butter, peanut butter, and eggs to room temperature makes it easier to blend the ingredients. Be sure to grind the peanuts, since whole, and even chopped peanuts tend to slip out of the dough. If using unsalted butter, increase salt to 1 teaspoon. Keep finished cookies refrigerated in airtight container. To restore just-baked chewiness, wrap a cookie in a sheet of paper towel and microwave for approximately 25 seconds. Cool before serving.