Heat the oven to 350°F. Grease a round pan so the cookie does not stick.
Mix the butter and sugar in a bowl until smooth and creamy.
Add the egg and vanilla. Stir until the mixture looks thick and shiny.
Add the flour, baking soda, and salt. Mix just until no dry flour is left.
Stir in the chocolate chips. The dough should be thick and easy to press.
Press the dough evenly into the pan. Smooth the top with a spoon.
Bake until the edges are golden and the center looks set but soft.
Let the cookie cake cool in the pan for at least 15 minutes before slicing.
Add frosting around the edge or on top if you want. Finish with sprinkles.