Preheat your oven to 350°F.
Combine the peanut butter, sugar, egg, vanilla extract, baking soda, and salt in a large mixing bowl. Mix until well combined.
Scoop 2 tablespoon-sized amounts of dough and roll them into balls. Place them directly on a baking sheet, spacing them about 2 inches apart. Gently press down on each ball to flatten slightly.
Bake in the oven for 10-12 minutes or until the edges are slightly golden.
Remove from the oven and allow the cookies to cool on the baking sheet for about a minute.
Melt the chocolate chips in the microwave, heating in 30-second intervals and stirring in between until smooth. If you have a piping bag, transfer the melted chocolate to the bag fitted with a small round tip. If not, transfer it to a plastic baggie and snip the corner.
Add a small dot of melted chocolate to the center of each cookie. Place two mini peanut butter cups on top of each cookie, pressing them slightly into the melted chocolate.
Place a dab of melted chocolate on the back of each candy eye and press them onto the peanut butter cups.
Squeeze the melted chocolate onto the cookies to create spider legs.
Allow the chocolate to set before serving. Enjoy your spooky treats!