For the cookies: Preheat the oven to 325 degrees F. Grease a baking sheet or line it with parchment paper.
Mix together the vanilla and eggs in a small bowl. Place the peanut butter in a large bowl and pour in the egg-vanilla mixture. Stir with a sturdy spoon until combined. Add the sugar and salt and mix well. Scoop the dough with a spoon and roll it into balls with your hands. The size of the scoop of dough is up to you, depending on the size cookies you prefer (the dough doesn't spread too much). Place the balls 2 inches apart on the baking sheet. Pat the balls flat and use a fork to make crosshatch marks on the top of each cookie. Bake until the centers look as light and baked as the edges, about 10 minutes. Cool completely before removing from the baking sheet with a spatula.
For the peanut butter filling: Put the brown sugar in a bowl and mash it with a fork to remove any lumps. Add the peanut butter and mix well with a sturdy spoon. Store in a covered container in the fridge until ready to use.
For the chocolate ganache filling: Melt the chocolate and heavy cream together, using a double boiler or saucepan. Be sure to watch carefully and stir often. As you go, your ganache can easily be made a little thicker or thinner as needed, by adding a bit more chocolate or a bit more cream.
For assembly: With a spoon or your fingers, scoop a spoonful of peanut butter filling and place it on the underside of a cookie. I like to use my hands to make a little "peanut butter patty" as if I were making a little hamburger on a bun. If you're making pb and j, spread jam on a second cookie. Top with the second cookie to make a sandwich.
For peanut butter and chocolate sandwich cookies, spread or spoon a healthy dollop of chocolate ganache on the underside of a cookie. Top with a second cookie to make a sandwich.
Let the cookies set for a while, either out on your kitchen counter or put them in the fridge to give the chocolate, if using, a chance to firm up. Then eat and share with all your favorite people.
Cook's Notes: Equal parts peanut butter and sugar is great for the filling, and so is 1 part sugar to 2 parts peanut butter. This filling keeps very well and can be used over a few weeks.
An alternative way to melt the chocolate is to use the microwave. Zap the chocolate and cream for just 30 seconds, then give it a good stir to help melt the chocolate. Continue to zap as many times as needed, sticking it in again for 15 to 20 seconds at a time.
NotesThis recipe was provided by a chef, restaurant or culinary professional and makes a large quantity. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.