Preheat and prep: Heat oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats. This helps prevent sticking and promotes even browning.

Cream the butter and sugars: In a large bowl, beat the softened butter, granulated sugar, and brown sugar together until smooth and slightly fluffy, about 2–3 minutes. This step helps create a tender, chewy texture.

Add eggs and vanilla: Beat in the eggs one at a time, mixing just until combined. Add vanilla and mix again. Avoid overmixing at this stage to keep the cookies soft.

Whisk the dry ingredients: In a separate bowl, whisk the flour, cocoa powder, baking soda, baking powder, and salt. Break up any cocoa lumps so the dough mixes evenly.

Combine wet and dry: Add the dry ingredients to the wet ingredients in two additions, mixing on low or by hand until just combined. The dough will be thick and chocolatey.

Fold in the chips: Stir in the semisweet chips and, if using, the milk chocolate chips. Reserve a small handful for topping if you want a bakery-style look.

Scoop: Use a medium cookie scoop (about 1 1/2 tablespoons of dough) and place mounds 2 inches apart on the prepared sheets. Press a few extra chips on top and sprinkle lightly with flaky salt if you like.

Bake: Bake 9–11 minutes, until the edges look set and the centers appear slightly soft and puffy. They will continue to set as they cool.

Cool: Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely. This helps lock in the chewy middle.

Enjoy: Serve warm for melty centers or let cool for a firmer bite. Either way, they’re chocolate heaven.