Make Grand Marnier syrup by combining sugar and water in a saucepan and heating, stirring occasionally, till sugar is dissolved.

Add Grand Marnier and cool to room temperature.

Heat the egg yolks and the ¾ cup sugar in a double boiler, whisking constantly until thick and doubled in volume.

Remove from the heat and continue whisking for a minute.

Set aside.

In a mixer bowl, beat the heavy cream, mascarpone and vanilla till thick and smooth.

Add the yolks and fold together till well combined. Set aside.

Dip one ladyfinger at a time into the syrup and lay on the bottom of a medium-sized baking dish. Layer with half the custard, then arrange about ¾ of the strawberry slices over the custard.

Repeat with a second layer of soaked ladyfingers and then top with the remaining custard.

Chill for several hours before serving.

Scoop out spoonfuls of tiramisu to serve.