Preheat oven to 375 degrees F.

In a mixing bowl, cream together butter, shortening, peanut butter, ½ cup granulated sugar, and brown sugar until light and fluffy, about 2 minutes.

Add eggs one at a time, mixing after each addition. Mix in the vanilla.

In a separate bowl, whisk together flour, baking soda, and salt.

Stir dry ingredients into the wet ingredients and mix gently to combine. Do not over-mix; the dough will be very soft.

Pour remaining ½ cup of granulated sugar into a small bowl.

Line a cookie sheet with parchment paper.

Scoop dough into balls and roll in sugar.

Bake for 7-10 minutes, just until set. The cookies will be pale and look barely set; do not over-bake.

Remove from oven and allow to cool on the baking sheet for 2-3 minutes, then transfer to a cooling rack.

Press an unwrapped Reese's heart into the center of each warm cookie.

Allow cookies to cool completely.