Gently rinse the fresh strawberries under cold water, then pat them dry with a paper towel. Reserve four strawberries for garnish, and chop the remaining ones into small pieces.

In a microwave-safe bowl, melt the dark chocolate using short bursts of heat. Stir after each interval until it's silky smooth. Allow the chocolate to cool slightly.

In a large mixing bowl, pour in the cold heavy cream and whip it with a hand mixer until soft peaks start to form. Gradually add in the powdered sugar while continuing to whip until the cream reaches stiff peaks.

Carefully fold the slightly cooled melted chocolate and vanilla extract into the fluffy whipped cream.

Fold the chopped strawberries into the mousse mixture.

Spoon the mousse into individual serving dishes or glasses, then refrigerate for at least two hours.

Top each serving with the reserved whole strawberries for a beautiful presentation.