Preheat the oven to 325 F and grease a mini-muffin pan.
In a large mixing bowl beat together the butter, peanut butter, granulated white sugar, and brown sugar. Beat in egg and vanilla.
In a separate bowl, mix the flour, baking soda, and salt. Gradually add the flour mixture to the sugar mixture.
Use a cookie scoop to measure out 1-inch dough balls. Roll gently in your hands and add 1 ball to each muffin well.
Bake in preheated oven for 11 minutes. Remove from oven and gently push a miniature Reeses cup into each cookie. Bake for another 4 minutes, or until light golden brown and the surface of the candies are beginning to melt.
Remove from oven and allow to cool in the pan for 10 minutes. Remove from cups using a spoon and cool on wire racks.
One 10.5 ounce family-sized bag should be enough for this recipe. They'd also be great with the white chocolate or dark chocolate mini peanut butter cups!
Depending on how much dough you put into each mini muffin well will determine how many cookies you get from this recipe.