Make ganache: Heat cream until simmering, pour over chopped chocolate, stir until smooth, chill for 20 minutes, scoop into 10 balls, and freeze for 10 minutes.
Preheat oven: Set to 350°F (175°C). Line a baking sheet with parchment.
Make dough: Cream butter and sugars. Add egg and vanilla. Whisk flour, cocoa, baking soda, and salt, then combine with wet ingredients. Fold in chocolate chips if using.
Assemble: Flatten 2 tbsp dough, wrap around a ganache ball, roll into a ball, and place on the baking sheet, 2 inches apart.
Bake: Bake 10-12 minutes until edges are set. Cool on the sheet for 5 minutes, then transfer to a rack.
Serve: Serve warm with ice cream or powdered sugar.