Preheat oven to 350 degrees F. Line cookie sheets with parchment paper or non-stick baking mat.
In a large mixing bowl, combine sugar, sour cream, egg, butter, & vanilla. Add flour, baking powder, & baking soda. Mix it up until a soft dough forms.
Place dough onto prepared cookie sheet & use your hands to press the dough out into a heart shape ΒΌ-1/2" thick.
Bake for 12-16 minutes or until edges are golden brown & middle is set.
Let cookie cool completely.
Mix up frosting by combining all the ingredients in a mixing bowl & using an electric mixer to mix it until smooth. *(You may need to add a little more powdered sugar or milk to get the right consistency).
Frost & decorate as desired.
Recipe by THE SEMISWEET SISTERS at https://www.thesemisweetsisters.com/2021/02/14/giant-heart-shaped-sugar-cookie-frosted/