Microwave the butter for about 40 seconds, just until it’s fully melted and smooth. It should be liquid but shouldn’t be hot—warm butter can affect the dough’s texture, so let it cool slightly.
In a medium bowl, whisk the flour, baking soda, baking powder and salt together. Set aside.
Take another large bowl, whisk the melted butter, brown sugar, and granulated sugar together until light and fluffy (2–3 min).
Add egg and vanilla; mix until smooth.
Pour into all dry ingredients and mix together gently with a spoon or spatula until just combined. The dough will be soft, thick, and slightly shiny. It should feel tender and a bit sticky, but not overly so.
Add chocolate chips and mix well.
Wrap the dough tightly and chill it in the refrigerator for at least 2 hours. For best results and to avoid cookies spreading too much, I strongly suggest letting the dough rest overnight.
Preheat the oven to 325°F (163°C). Line the baking sheet with parchment paper or silicone baking mats. Scoop 2 tbsp or (40g per cookie) dough balls onto a lined tray, spaced 5 cm apart. If the dough has been chilled for more than 2 hours, allow it to sit at room temperature for about 15 minutes before baking.
Bake for 9–11 minutes, until the edges turn golden and the centers remain soft. The cookies will be slightly puffy and may look a bit underdone in the middle. I sometimes press extra chocolate chips into the tops—it’s optional, but it makes the cookies look bakery-perfect.