Preheat oven to 350°F/178°C. Line a large baking sheet, or cookie sheet with parchment paper.

To a mixing bowl (if using a hand whisk) or stand mixer, add the butter and both sugars. Mix until the sugars are dissolved into the butter, about 2 minutes. Add the vanilla and egg, mix until well combined, scraping the sides of the bowl until well mixed.

Sift in the flour, baking soda, baking powder and ¼ teaspoon salt. Mix just until the flour is incorporated. Add the chocolate chunks and use a spatula to mix them in. Refrigerate for 30 minutes or freezer for 15 minutes. This allows the butter to firm up and prevent the cookies from spreading too much.

Scoop 2 tablespoons of dough and place onto the cookie sheet, 3-inches/8 cm apart. If you want to really make sure they are all the same size, weigh them to 1.2 ounce/34 grams each. Use the palm of your hand to flatten the top slightly and add more chunks if needed.

Bake for 16-18 minutes, the time may be shorter if your baking pan is darker in color. The edges should be golden brown. Remove from the oven and immediately sprinkle a light coverage of flaky sea salt.

Cool the cookies on the pan for a few minutes. Transfer to a baking rack and cool completely. They will keep for up to 4 days in a sealed container at room temperature.