Preheat oven to 325ºF. Line baking sheets with parchment paper.
Place the butter and sugar in a stand mixer and beat until light and fluffy, scraping down mixer bowl occasionally, about 3 full minutes. Beat in vanilla extract. Incorporate flour with mixer speed on low.
Scoop dough by a heaping tablespoonful into your palm and roll into a ball. Make a small indent with your index finger. Transfer to prepared baking sheet. Repeat with remaining dough.
Bake for 12 minutes then remove from oven and top each cookie with a piece of chocolate. Return to oven and bake for 2-4 minutes more, until chocolate starts to melt and cookie starts to turn golden at the edges.