1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius). Line muffin trays with paper cups.
2. In the bowl of an electric mixer, beat the sugar, butter, and oil until fluffy and lighter in color.
3. Add the flour, baking powder, salt, vanilla, and eggs and beat until well combined.
4. In a separate bowl, dissolve the coffee granules in boiling water. Add the cocoa and chocolate syrup and mix until combined.
5. Add one cup of batter to the chocolate mixture and mix until well combined.
6. Divide the white batter among the lined muffin cups.
7. Add a few chocolate balls or chocolate-coated cornflakes.
8. Top with a few spoonfuls of chocolate batter. Swirl gently with a knife to combine.
9. Place a few more chocolate balls or chocolate chunks on top, if desired. Bake for 25 minutes.