Prepare the Chocolate: Place the finely chopped bittersweet chocolate into a medium-sized, heatproof bowl.
Set aside.
Heat the Cream: Pour the heavy cream into a small saucepan and heat over medium heat.
Bring it just to a simmer, watching for small bubbles to form around the edges.
Do not let it come to a rolling boil.
Combine and Rest: Carefully pour the hot cream directly over the chopped chocolate.
Let the mixture sit undisturbed for 5 minutes. This allows the hot cream to gently melt the chocolate.
Whisk to Perfection: Starting from the center of the bowl, gently whisk the mixture in small circles, gradually moving outwards.
Continue whisking until the ganache is completely smooth, glossy, and emulsified.
Use or Cool: Use immediately as a warm glaze or sauce. For a thicker consistency or a whipped frosting, let it cool to room temperature (about 1-2 hours), then whip with an electric mixer until light and fluffy.