In a large bowl, cream butter, brown sugar, and oil. Add eggs one at a time.
Mix in sour cream, heavy creamy, vanilla, baking soda, espresso powder, and salt. Stir in cocoa powder.
Add flour around ½ cup at a time until just combined. Do not overmix.
Fold in chocolate chips.
Chill cookie dough for at least an hour.
Preheat oven to 350.
Line baking sheets with parchment paper or spray with nonstick cooking spray. Using a cookie scoop drop dough onto pan. I used a 2 teaspoon #100 scoop.
Bake for 8-10 minutes until they're just set. Cook on pan for 2-3 minutes. Remove to wire rack to cool completely.
For the Frosting
Fill a double boiler with water. Place chocolate chips into top of the double boiler and cook over medium heat stirring occasionally until melted.
Stir in sweetened condensed milk and cook for 2 more minutes until shiny.
Frost cookies and top with a pecan half if desired. Enjoy!