Preheat oven to 350°F. Line two baking sheets with parchment paper or silicone liners. Pour the sparkling sugar onto a plate.
In a separate bowl, beat butter, granulated sugar and brown sugar for 2 minutes, until smooth and creamy. Add egg, egg yolk, and molasses and beat until thoroughly combined, scraping the sides of the bowl as needed. Add the flour mixture and beat until combined.
Scoop the dough into balls (see note) and roll the balls of dough in the sparkling sugar (be generous!). Place the dough balls on prepared baking sheets at least 2 inches apart, they will spread quite a bit. Bake for 8-12 minutes (see note). Be careful not to overbake. The center of the cookie should still look slightly underdone when you pull them from the oven. Place the baking sheets on wire racks to cool completely.
Adapted from All Recipes