I unwrap about two dozen mini peanut butter cups and pop them into the freezer while I preheat my oven to 350°F. Freezing them firms them up so they hold their shape once pressed into a warm cookie. This little trick makes a noticeable difference in how neat the finished spiders look.
In a large bowl, I beat the softened butter with both sugars using an electric mixer until the mixture turns pale, smooth, and fluffy. This usually takes about a minute. Creaming properly here traps air in the dough, which keeps the cookies tender instead of dense.
Next, I mix in the peanut butter, egg, and vanilla extract, beating just until everything is fully incorporated. The dough will look glossy and slightly thick at this point. I always scrape down the sides of the bowl so nothing gets left unmixed.
I add the flour, baking soda, baking powder, and salt directly into the wet mixture, stirring on low speed or by hand with a spatula. I stop as soon as no dry streaks remain, since overmixing can make the cookies tough instead of soft.
Using a small cookie scoop, I portion out tablespoon-sized balls of dough, roll them smooth between my palms, and coat each one in granulated sugar. I space them two to three inches apart on a lined baking sheet and bake for eight to eleven minutes, until the edges just begin to crack.
As soon as the cookies come out of the oven, I press a frozen mini peanut butter cup right into the center of each one. I let them rest on the baking sheet for fifteen to twenty minutes before moving them, since disturbing them too early can cause the candy to sink.
Once the cookies are fully cool, I melt the chocolate chips with a touch of neutral oil in the microwave, stirring every thirty seconds until smooth. I transfer the melted chocolate into a squeeze bottle and pipe four thin legs on each side of every cookie.
Finally, I dab a small amount of melted chocolate onto the back of two candy eyeballs and press them onto each peanut butter cup while the chocolate is still soft. I let everything set completely before serving or stacking the cookies.