Preheat the oven to 375 degrees F, adjust the racks close to the center. Prepare muffin tins with approximately 16 paper cups.In a large mixing bowl, combine softened butter with ½ cup of the sugar, 2 tablespoons of the espresso powder and salt. Mix just until everything is evenly incorporated. Add the egg and use a whisk to blend it into the batter. Now add the half and half and vanilla and mix until smooth.Add the flour and baking soda and mix just until you no longer see dry spots. Then fold in the mini chocolate chips.Fill each muffin cup about ¾ the way up with the batter. (This is easily done with an ice-cream scoop.)In a small bowl, mix the remaining 2 tablespoons of sugar with the remaining ½ teaspoon of espresso powder. Generously sprinkle this mixture evenly over the muffin batter in each cup.Bake in the preheated 375 degree F oven until they’re set, about 18 minutes.Let them cool in the muffin tins for at least 15 minutes before serving.