Cream-Filled Chocolate Cupcakes

Preheat the oven to 350°F and line a muffin pan with paper liners, preparing a second pan or baking in batches if needed.
Combine the flour, cocoa powder, baking soda, baking powder, and salt in a large bowl until evenly mixed.
In a separate bowl, whisk together the oil, sugar, egg, vanilla, and buttermilk until smooth.
Pour the wet mixture into the dry ingredients, add the hot coffee or water, and whisk until a thin batter forms.
Divide the batter evenly between liners, filling each about two-thirds full.
Bake until the cupcakes spring back lightly and a toothpick inserted in the center comes out clean.
Let the cupcakes rest briefly in the pan, then transfer them to a rack to cool completely before filling.
Place the chopped chocolate in a heat-safe bowl and heat the cream until just beginning to steam, then pour it over the chocolate.
Allow the mixture to sit briefly, then stir slowly until smooth and glossy before chilling until thickened.
Beat the softened butter until creamy, then add powdered sugar, cream, vanilla, and salt, whipping until light and fluffy.
Cut a small circle from the center of each cooled cupcake to create a cavity for the filling.
Spoon or pipe the vanilla cream into each cupcake, then replace the trimmed cake tops.
Spread a generous layer of thickened ganache over each cupcake, creating a smooth, rich topping.
Pipe additional buttercream decoratively on top if desired, then serve or chill until ready to enjoy.