Preheat the oven to 375°F. Lightly grease two baking sheets, or line with parchment., Beat together the butter, sugars, vanilla, salt, baking powder, and baking soda till well combined and lightened in color., Add the egg, beating till smooth. Scrape the sides of the bowl, and beat again till smooth., Add the flour, mixing it in completely., If you're making cookies using chips, nuts, etc, beat in the milk, then the add-ins. If you're making plain cookies, without add-ins, omit the milk., Drop the cookies by the generous tablespoon onto the prepared baking sheets, spacing them about 2" apart. A tablespoon cookie scoop works well here., Bake the cookies for 10 to 14 minutes (or up to 16 minutes; ovens may vary). The cookies should be a light golden brown, and a bit darker around the edges. For softer cookies, bake the shorter amount of time; for crunchy cookies, bake longer., Remove the cookies from the oven, and cool right on the baking sheets., Store these chocolate chip cookies airtight at room temperature for several days. Freeze for longer storage.