Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, combine butter with brown sugar until fluffy. Add in egg and vanilla extract and mix until smooth.
Add in the flour mixture, mix until it is fully combined. Roll the cookie dough into balls, and place them onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes.
Remove from the oven, and place one heart chocolate on each cookie.