Preheat the oven to 350°F (175°C).
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy.
Add the eggs one at a time, followed by the vanilla extract, and mix until fully incorporated.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry mixture to the wet ingredients, mixing until just combined.
Fold in the mint chocolate chips and peppermint extract if using.
Scoop tablespoon-sized portions of dough onto a parchment-lined baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes or until the edges are lightly golden brown.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack.