In the bowl of a stand mixer fitted with a paddle attachment, or a handheld mixer, cream together butter, brown sugar, and white sugar for 5 minutes on medium speed until light and fluffy.
Once five minutes is over, add in egg and vanilla and mix until combined.
In a separate bowl, mix flour, baking soda, and salt, and mix until combined. Add these dry ingredients to the butter mixture on low speed, and mix until just combined.
Using a wooden spoon or spatula, mix in chocolate chips or chunks until just combined. Place bowl of dough in fridge for at least 30 minutes to chill.
While dough is chilling, heat oven to 180 C (350F). Portion dough out into heaped 1 tbsp-2 tbsp sized dough pieces on parchment paper lined baking sheets. Bake for 11-12 minutes or until golden brown on the edges but still soft in the center. Cool until cookies firm up, then enjoy, still warm.