Begin by gathering all your ingredients and letting the butter soften at room temperature.
In a large mixing bowl, combine the softened butter and sugar. Beat them together on medium speed until light and fluffy (about 3-4 minutes).
Add the orange zest and vanilla extract to the butter-sugar mixture and mix until well incorporated.
In a separate bowl, whisk together the flour and salt. Gradually add the dry ingredients to the butter mixture, mixing on low speed until just combined.
Gently fold in the chopped dark chocolate using a rubber spatula.
Form the dough into a log shape, wrap in plastic wrap, and refrigerate for at least 1 hour.
Preheat your oven to 350°F (175°C) while the dough is chilling. Line a baking sheet with parchment paper.
Once the dough is firm, slice it into 1/4-inch thick rounds and place on the prepared baking sheet.
Bake for 12-15 minutes, or until the edges are lightly golden.
Let the cookies cool on the baking sheet for 5 minutes before transferring to a cooling rack.
