Chop the semisweet chocolate into small pieces and place in a heatproof bowl.
In a saucepan, heat the heavy cream over medium heat until it begins to simmer.
Pour the hot cream over the chopped chocolate.
Let it sit for about 5 minutes to soften the chocolate.
Stir the mixture gently with a spatula until smooth and fully combined.
Add the butter and vanilla extract, stirring until fully melted and incorporated.
Allow the ganache to cool at room temperature until it thickens to your desired consistency.
Use the ganache for frosting, filling, or drizzling over desserts.