Preheat and prepare:
Heat your oven to 350°F (175°C). Generously grease an 8-inch baking pan and line it with parchment paper.

Mix wet ingredients:
In a medium bowl, combine the granulated sugar with the vegetable oil, milk, and vanilla extract. Beat together until well mixed. Add the egg and beat just until combined, about 30 seconds.

Combine dry ingredients:
In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking soda, and salt.

Bring it all together:
Add the dry ingredients to the wet mixture and stir just until combined. Fold in the semi-sweet chocolate chips gently with a spatula.

Bake:
Spread the batter evenly into the prepared pan. Sprinkle extra chocolate chips on top and bake for 25–30 minutes. A toothpick inserted in the center should come out damp but not wet or gooey.

Cool and serve:
Remove from oven and let the brownies cool completely in the pan before slicing. Garnish with flaky sea salt if desired.