Preheat the oven to 425°F and prepare muffin tins with paper liners.
In a large bowl, combine 1 cup white sugar, 6 tablespoons melted unsalted butter, and ¼cup vegetable oil. Mix or whisk together.
Add in 1½ cups whole milk, 2 large eggs, and 1 teaspoon vanilla extract.Blend to combine.
Next, mix in 2½ cups all-purpose flour, ½ cup unsweetened cocoa powder,and 1 tablespoon baking powder just until there are no large flour lumps; becareful not to over-mix as it will make the muffins dense.
Add ½ cup mini chocolate chips into the batter and gently stir them in.
Pour the batter into each hole of the prepared muffin tin until full.
Top with additional chocolate chips or coarse sugar if desired.
Bake at 425°F for 5 minutes then reduce the temperature to 350° F and bake for an additional 15 minutes.
After baking transfer the muffins to wire rack to cool completely.
Once cooled store them in airtight container at room temperature for up to 3 days or up to 5 days if refrigerated.
