Preheat the oven to 375F. Line two baking sheets with parchment or silicone liners.
In a medium bowl or the bowl of a stand mixer, beat the butter and sugar until light and fluffy. Add the vanilla and egg yolk, and mix until smooth. Add the flour and salt, and mix to form a thick dough.
Roll the dough into one inch balls and place on prepared baking sheets. Use your finger to press down twice on each ball, making a heart-shaped indent. Place two gummy bear halves into each indent in a v shape.
Bake for 9-11 minutes, or until the cookies are just slightly golden at the bottom and the gummy bears are melty. If the gummy bears do not melt all the way, use a toothpick to gently spread them throughout the indent in the cookie.