For the chocolate syrup: In a small bowl, combine hot water, cocoa powder, 2 tablespoons sugar, and liqueur. Set aside to cool slightly.
For the chocolate ganache: Place chopped chocolate and cream in a medium heat-proof bowl. Carefully microwave in 20-second intervals, stirring in between each interval, until melted. Alternatively, set it over a saucepan of simmering water, stirring occasionally. Set aside to cool slightly.
For the filling: In a large bowl, place mascarpone and vanilla extract and whisk vigorously until creamy and smooth (there’s no need to use the mixer for this). In a different mixer bowl, using an electric mixer, whisk together heavy cream and sugar until stiff peaks form. Fold whipped cream into mascarpone in 2 additions until mixture is smooth.
Assemble tiramisu: Dip ladyfingers very quickly (less than a second) into the chocolate syrup. Break each one into 4 pieces and place them at the bottom of the glasses (you don’t have to use all 4 pieces at once; it depends on the size of the glass.). Spoon a dollop of the mascarpone cream mixture on top. Add a thin layer of chocolate ganache, about 1-1.5 teaspoons, on top of the mascarpone cream. Repeat once more and finish with another layer of mascarpone cream. Dust the top with cocoa powder or grated chocolate.
Refrigerate for at least 1-2 hours until set. Tiramisu will keep for 3 days in the fridge.