Preheat your oven to 350°F (175°C).
Line two cookie sheets with parchment paper.
In a double boiler or a microwave-safe bowl (heating in 30-second intervals), gently melt half of the chocolate chips (1 cup / 170g).
Set aside to cool slightly.
In a large bowl, use an electric mixer to cream the softened butter with the granulated and brown sugars until the mixture is light, pale, and fluffy, about 2-3 minutes.
Beat in the slightly cooled melted chocolate and the vanilla extract until everything is well combined.
In a separate medium bowl, whisk together the flour, baking soda, and salt. Gradually add the dry to the wet , mixing on low speed until just combined. Be careful not to overmix.
Using a spatula or wooden spoon, fold in the remaining 1 cup (170g / 6 oz) of chocolate chips.
Drop rounded teaspoonfuls (or use a small cookie scoop) of dough onto the prepared cookie sheets, placing them about 2 inches apart.
Bake for 15 to 17 minutes, or until the edges are golden brown and the centers are set. Be careful not to overbake for a chewier texture.
Let the cookies cool on the baking sheet for 2-3 minutes before transferring them to a wire rack to cool completely. Store in an airtight container at room temperature.
Don't overmix the batter once you add the flour.
Mix only until the flour streaks disappear to ensure a tender, not tough, cookie.
