Preheat to 350°F. Prepare tulip or standard muffin liners in a muffin tin.
Whisk sugar, egg, oil, coffee, vanilla, and salt until smooth.
Sift in baking soda, cocoa, and flour. Pour in buttermilk. Stir to combine.
Divide batter into 4 tulip liners or 6 standard liners. Add chocolate chunks on top.
Raise oven temp to 425°F. Bake 7 minutes. Lower to 350°F. Bake 10–12 minutes.
Let cool 10 minutes. Use paring knife to remove muffin centers.
Pour hot cream over chopped chocolate. Let sit 2 mins, then stir smooth.
Pipe ganache into centers of muffins. Cap and serve.
