In a large bowl, cream together the butter, sugar and corn syrup. Add in the egg and vanilla and mix until fully combined.
In a separate bowl, mix together the flour, salt, and baking soda. Slowly mix the dry ingredients into the wet ingredients until fully incorporated. Fold in the peppermint chunks.
Place the cookie dough in the fridge for at least 6 hours.
Preheat the oven to 350˚F. Line 2 baking sheets with parchment paper.
Using a cookie scoop, scoop the batter onto the prepared baking sheets. Bake in the preheated oven for 10-15 minutes,or until the edges are lightly brown. Allow the cookies to cool completely on the baking sheet.