Preheat the oven to 350°F. Spray 2 cookie sheets with nonstick spray, or line with parchment paper.
On a sheet of waxed paper or in a medium bowl, sift together flour, cocoa and salt.
In a large bowl, with an electric mixer, beat the butter, cream cheese, granulated sugar, and brown sugar until creamy. Beat in the vanilla. Beat the flour mixture into the butter mixture. With your fingers, knead in the chocolate chips.
Divide the dough into quarters. Divide each quarter into 6 equal pieces. Roll each piece of dough into a ball and place on the prepared cookie sheets. Repeat to form 24 balls.
Using the bottom of a glass, press the balls into 2-inch rounds. (See tip below.)
Bake cookies in two batches, for 8 minutes, or until slightly puffed and very soft to the touch. Let cool on the pans for 1 minute, then transfer to wire racks to cool before serving.
Notes
To prevent glass from sticking when you flatten the balls of dough, coat the bottom of the glass with granulated sugar. Dip glass in water, then into a saucer of sugar. After you've flattened the first cookie, the glass will become sticky and the sugar will adhere to it.