Prepare the tiramisu
1. In a large bowl, mix the mascarpone with powdered sugar and vanilla extract until smooth.
2. In a separate bowl, whip the heavy cream until stiff peaks form, then gently fold it into the mascarpone mixture.
3. Pour the raspberry juice or raspberry liqueur into a shallow dish. Quickly dip the speculoos cookies in it so they are slightly soaked but not too soft.
4. In a baking dish, layer the soaked speculoos cookies. Spread a layer of the mascarpone cream on top and add a layer of raspberries.
5. Repeat the process until all ingredients are used, making sure the last layer is mascarpone cream.
6. Chill the tiramisu in the refrigerator for at least 4 hours, preferably overnight.
7. Before serving, dust with cocoa powder and garnish with fresh raspberries.