Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, mix together butter, peanut butter and both sugars until fluffy. Add in egg and vanilla extract and mix until smooth.
Add in the flour mixture, and mix until it is fully combined. Fold in the Reese's pieces. In a shallow dish, combine granulated sugar and ground cinnamon.
Roll the cookie dough into balls and roll in the sugar mixture. Place cookies onto a large ungresaed baking sheet at least 2-inches apart. Bake for 10-12 minutes. Remove from the oven and top with chocolate hearts.
