Preheat your oven to 350°F (175°C). In a mixing bowl, combine the all-purpose flour, softened butter, and sugar until resembling coarse crumbs. Press into a tart pan. Bake for 15-20 minutes until golden brown, then cool completely.

Melt the white chocolate in a double boiler or microwave until smooth, then allow it to cool slightly.

Beat the heavy cream in a large bowl until soft peaks form (3-4 minutes).

In another bowl, beat the eggs until pale and fluffy. Fold the melted white chocolate into the eggs, then gradually fold in whipped cream.

Pour the mousse mixture into the cooled tart shell, smoothing the top.

Cover the tart with plastic wrap and refrigerate for at least 40 minutes until set.

Unclip the tart pan and transfer to a serving plate. Garnish with berries, chocolate shavings, or mint leaves.