Adjust oven rack to middle position and preheat oven to 375°F. Spray standard muffin tin with non-stick pan spray. Sift flour, cocoa, baking powder, baking soda, and salt into medium bowl; set aside. In large bowl, whisk sugar with eggs until light, about 30 seconds. Whisk in oil, milk, vanilla, and espresso until combined.
Whisk dry mixture into wet mixture until just combined. Stir in 1 cup chips.
Evenly divide batter between muffin cups and sprinkle with remaining chips. Bake until set, 17 to 19 minutes. Let muffins cool in pan 15 minutes, then remove muffins from tin and place on wire rack to cool.