In a large mixing bowl, beat together the mascarpone cheese and powdered sugar until smooth. In a separate bowl, whip the heavy cream until stiff peaks form. Fold the whipped cream into the mascarpone mixture.

Pour brewed coffee into a shallow dish and allow it to cool. Quickly dip each ladyfinger into the coffee and arrange them in a single layer in a rectangular serving dish. Spread half of the whipped mascarpone mixture over the ladyfingers.

Lay half of the fresh raspberries over the mascarpone layer and gently press them into the cream mixture.

Repeat the process by layering the remaining ladyfingers in coffee on top of the raspberries and then spread the rest of the mascarpone mixture over the ladyfingers. Finish with a layer of the remaining raspberries.

Cover the assembled tiramisu and refrigerate for at least 2 hours before serving. Garnish with additional raspberries and a dusting of powdered sugar.