Preheat oven to 375 degrees F. Line baking sheets with parchment or a silicone baking mat.
In a small bowl, whisk together the flour, salt and baking soda.
In a mixing bowl, combine the peanut butter, shortening, brown sugar, milk and vanilla. Beat at medium speed until well blended, about 2 to 3 minutes. Add the egg and beat just until blended. Reduce speed to low and add the dry ingredients to the creamed mixture gradually, mixing just until combined.
Put the granulated sugar in a small bowl. Scoop a tablespoonful of dough and roll into a ball between the palms of your hands. Roll the dough into the sugar and place on the baking sheet, about 2 inches apart. Dip the tines of a fork into the sugar and make a crisscross pattern on the cookies, flattening them slightly.
Bake for 7 to 8 minutes or until set and just beginning to brown. Cool 2 minutes on baking sheet before removing to a wire rack to cool completely. The cookies can be stored in an airtight container at room temperature for up to 1 week or frozen for up to 3 months.
Preparing your pans - Whether you use cookie sheets or rimmed baking sheets, be sure that your sheets are ungreasedor lined with parchment to keep the cookies from spreading and absorbing too much grease.
Can you use butter instead of shortening? In a word, no. Shortening keeps the cookies from spreading too much, keeps them from being crumbly, and ensures that they are nice and soft. Replacing it with butter would significantly alter the texture of the cookies and I beg you not to do it. They do now make butter-flavored shortening that I've used from time to time if you're worried about the flavor.
Peanut Butter - It is important to use traditional, processed peanut butter (i.e. Jif, Skippy, Peter Pan, etc.) in this recipe. Using natural peanut butter that has oil separation will be much too greasy and cause the cookies to spread and become crumbly, so I do not recommend using natural peanut butter.
Nut Butter Alternatives - You can use other nut butters such as almond butter, cashew butter, etc. as long as they do not have oil separation (see the note above). A great almond butter substitute that works exceptionally well in all baked goods I've tried it with is Barney Butter.
Avoid crumbly cookies - The three most common reasons peanut butter cookies end up crumbly are (1) too much flour; (2) using the wrong kind of peanut butter, and (3) they are overbaked. Be sure to either weigh your flour or spoon it into your measuring cup before leveling (the scoop method often results in too much flour), use the correct type of peanut butter (see above), and take the cookies out when the centers still look soft and underdone. They will set as they cool.
Fun Extras - You can jazz these cookies up a bit if you'd like! Try rolling in colored sugars for a festive look or add some mix-ins - try a ½ cup of chopped peanuts, mini chocolate chips, peanut butter chips, butterscotch chips, or any other mix-in you like to pair with peanut butter!
Make-Ahead - You can prepare the cookie dough and refrigerate for up to 3 days before baking. When ready, let it sit on the counter for about 30 minutes before scooping and proceeding with baking.
Storage - These cookies will keep in an airtight container at room temperature for up to 1 week.
Freezing Instructions - These cookies freeze exceptionally well! You can freeze the balls of dough in a ziptop plastic bag for up to 3 months. Remove from the freezer, let sit at room temperature for 30 minutes, then roll in sugar and make the crisscross pattern on top, then bake as directed, adding an extra minute. You can also freeze the baked cookies by wrapping them individually in plastic wrap, then place them in a ziptop bag and freeze for up to 3 months.