Small bowl of granulated sugar for rolling the cookie dough
Preheat oven to 350 degrees. Line two baking sheets with parchment paper.
In a small mixing bowl, combine the flour, baking soda, and salt. Set aside until ready to use.
In a large mixing bowl, cream together the butter, vegetable shortening, peanut butter, eggs, vanilla, brown sugar, and granulated sugar until fluffy.
Add the flour mixture to the creamed mixture, and beat until fully combined.
Roll the dough into 1” balls, and roll around in granulated sugar. Place the cookie dough balls about 2” apart onto the parchment paper lined baking sheet, and with a fork, press lightly to flatten each ball with a criss-cross pattern.
Bake for 10-12 minutes. Remove from the oven, and let sit for 3 minutes before removing from baking sheet. Cool completely on a cooling rack.
Fill a pastry bag with half peanut butter filling, and half chocolate fudge filling. Choose two cookies that are the same size, and begin filling them by piping the filling onto the bottom of one cookie, and top it off with the second cookie, making sure the the bottoms of the cookies are to the inside of the sandwich. Repeat with remaining cookies.
Store in a plastic container with a lid for up to a week (if they last that long!). Makes 3 dozen sandwich cookies.