Beat both sugars and butter together in a medium bowl with an electric mixer until creamy. Add egg, miso and vanilla and beat until well mixed. Add flour and baking soda and mix until just combined. Stir in chocolate chips. Cover with plastic wrap and refrigerate at least 1 hour (this is very important in order to have a chewy cookie that doesn't spread out too much).
Preheat oven to 350 degrees F. Spray 2 baking sheets with nonstick cooking spray.
Use a medium ice cream scoop to portion cookie dough on the prepared pans. Use two fingers to lightly flatten each scoop of dough. Bake, rotating and switching the pans halfway through, 13 to 14 minutes for a chewy cookie (a few minutes longer if you like a more well-done cookie). Eat warm with a glass of milk and cool the rest on a wire rack.