Preheat the oven to 180°C (350°F).
Crush the speculoos cookies into fine crumbs.
Mix the crushed cookies with melted butter.
Press the mixture into the bottom of a tart pan.
Bake the crust for about 10 minutes until golden.
In a bowl, whisk together mascarpone cheese, heavy cream, powdered sugar, and vanilla extract until smooth.
Gently fold in half of the raspberries into the cream mixture.
Spread the cream mixture over the cooled crust.
Top the dessert with the remaining raspberries.
Chill the dessert in the refrigerator for at least 2 hours before serving.
Garnish with mint leaves before serving, if desired.