Prep: Position oven rack in the center and preheat the oven to 175°C (350°F). Line two baking sheets with parchment paper or a reusable silicone mat. Pre-measuring ingredients saves time and keeps the process smooth.

Cream the butter and sugars: In a large mixing bowl, place the room-temperature unsalted butter (113 g), granulated sugar (100 g), and packed light brown sugar (110 g). Using a stand mixer with the paddle attachment or a handheld mixer set to medium speed, beat for 2–3 minutes until the mixture is pale and slightly fluffy. Why: Creaming incorporates air into the butter-sugar matrix, creating lift and a light texture; the brown sugar's molasses helps the cookie stay moist and chewier.

Add oil, egg, milk, and vanilla: Reduce the mixer speed to low. Pour in the neutral oil (28 g), the large egg, whole milk (60 ml), and vanilla (1 tsp). Mix until just combined. Why: The oil adds tenderizing fat that yields a softer crumb than butter alone; milk contributes moisture and a faint dairy richness. Mixing gently avoids over-incorporating air which can make cookies cakey.

Combine dry ingredients: In a separate bowl whisk together the all-purpose flour (300 g), baking soda (1 tsp) and fine sea salt (1/2 tsp). Whisking distributes the raising agent and salt evenly, ensuring uniform rise and seasoning throughout every cookie.

Fold dry into wet: Add the dry ingredients to the wet mixture in two additions, folding with a rubber spatula or mixing on very low speed until no dry streaks remain. Do not overmix. Why: Overmixing develops gluten and will make cookies tough — stop as soon as the dough comes together for a tender result.

Add chocolate chips: Fold in the semisweet chocolate chips (170 g) by hand so they’re distributed without overworking the dough. Why: Hand-folding prevents chip pulverization and helps you control distribution so each cookie gets good pockets of chocolate.

Chill (optional but recommended): Cover the bowl with plastic wrap and chill the dough for 30–60 minutes in the refrigerator. Why: Chilling firms the fat and allows the flour to hydrate; this slows spread during baking and concentrates flavor, yielding cookies with a thicker, chewier center and crisp edges.

Portion the cookies: Use a 1.5 tablespoon cookie scoop (or scale portions to roughly 28–30 g each) to portion dough onto the prepared baking sheets, spacing them about 2 inches apart. Slightly press additional chips on top of each mound for an attractive finish. Why: Uniform portions bake evenly; pressing chips onto the top gives a professional bakery appearance.

Bake: Bake one tray at a time on the center rack for 10–12 minutes, until the edges are golden and centers still look slightly underbaked. Rotate the tray halfway through if your oven runs hot. Why: Removing the cookies when centers still look a touch soft ensures they finish with a tender, chewy interior as they finish on the hot sheet outside the oven.

Finish and cool: Let the cookies cool on the baking sheet for 5 minutes (this allows residual heat to finish the bake and sets structure), then transfer to a wire rack to cool completely. If using, sprinkle a small pinch of flaky salt on warm cookies for a balanced sweet-salty contrast.

Storage: Once fully cooled, store cookies in an airtight container at room temperature for up to 5 days; place a slice of bread in the container to maintain softness (the bread rehydrates the cookies slightly). For longer storage freeze the baked cookies, well-wrapped, up to 3 months.