Preheat the oven to 375 degrees F.
Line several baking sheets with parchment paper or a silicone mat. Set aside.
In a large bowl or bowl of electric mixer, beat the butter until fluffy, about 30 seconds.
Add the brown sugar and granulated sugar, baking soda, and salt and beat until well combined.
Beat in the eggs and vanilla extract.
Add the cocoa powder and beat until well combined.
Gradually add the flour and mix well, scraping down the sides of the bowl.
Divide the dough with a cookie dough scoop or drop by tablespoon onto the prepared baking sheets.
Bake 8-10 minutes or until the edges are firm and the centers appear set.
Remove and transfer to a wire rack and cool completely.
In a small bowl, stir together the peanut butter and confectioner’s sugar until smooth.
In a small heavy saucepan, combine the chocolate chips and the shortening **see notes
Heat over low until chocolate is completely melted, stirring occasionally.
Frost tops of cookies with the melted chocolate and then place them on a baking sheet.
Place the frosted cookies in the refrigerator to chill until set, about 10 minutes.
Then top each cookie with a teaspoon of the peanut butter mixture. **see notes
Store in an airtight container in the refrigerator for up to 1 week.