Preheat oven to 350 degrees. Grease mini muffin pan and set aside.
In a medium bowl, stir together flour, baking soda, and salt. Set aside.
In the bowl of a stand mixer cream together shortening, peanut butter, and sugar until fluffy and light in color. About 90 seconds.
Add egg and vanilla extract to creamed peanut butter mixture. Mix well.
Slowly add in the flour mixture to the stand mixer and mix on low to combine well.
Using a 1 ½ tablespoon cookie scoop, scoop out dough and roll in a ball. Roll each ball in sugar then place in greased mini muffin pan.
Press one unwrapped mini peanut butter cup in to each cookie dough ball in the muffin pan.
Bake at 350 degrees for 9-10 minutes. Cookies will look set on edges but not brown up in color. Remove from oven and let cool completely in the pan. Once completely cool, remove cookies to a cooling rack.
Melt 1 ½ cup milk chocolate chips in 30 second incriments in the microwave stiring after each increment. Once smooth, transfter to a ziplock bag and cut off the corner to pipe on a drizzle of chocolate to each cookie after completely cooled and removed from muffin pan.
Store in air tight container at room temperature for 3-5 days or freeze up to 2 weeks.