Sift together flour and baking soda and set aside.
Cream together butter and sugars; mix in egg and vanilla then peanut butter. Stir in flour mixture a little at a time until everything is incorporated.
Chill dough for one hour.
Preheat oven to 375 F.
Line a cookie sheet with parchment paper.
Form chilled dough into balls, roll in colored sugar and place on cookie sheet.
Bake for 8-10 minutes. Remove from oven and allow to cool for a couple of minutes.
Press a frozen heart onto each cookie and refrigerate for 5 minutes before serving or storing.
