I know it's too late for the birthday party but I'll share my recipe to you nevertheless.
Tiramisu my style
For the pie crust
40 g butter
150 g sugar
100 g flour
100 g cornstarch
3 tsp baking soda
1 pk. Vanilla sugar
2 tablespoons hot water
For the Mascarpone Cream:
5 egg yolks
100 g of sugar
200 g mascarpone cheese (very fresh)
1 tablespoon lemon juice
3 tablespoons Grand Marnier
4 egg whites
100 g of sugar
100 ml whipping cream
For the Completition
3 espresso cups of espresso
Grand Marnier to taste (at least 3 tablespoons)
1. For the pie crust: Grease a springform pan of 10 inch diameter and dust with flour. Melt the butter in a small saucepan. Separate yolks and whites of the 3 eggs and pour into two mixing bowls.
2. Whisk yolks with 2/3 of the sugar and vanilla sugar using a hand mixer until cream is thick and whitish. Mix flour, baking powder and cornstarch together and sift onto the egg yolk cream. Add the liquid lukewarm butter and water. Stir in.
3.Beat egg whites until semi stiff , add gradually the remaining sugar and continue to beat the egg white until it is stiff and glossy. First stir in some of it to the egg yolk cream and then fold in gently the remaining egg white.
4. Pour the pie crust mixture into the prepared pan, smooth down, and bake in the oven at 356 °F for about 25 - 30 minutes. Overturn the still-warm pie crust on a round wire rack and cool down for about 60 minutes.
5. Mascarpone cream: Beat yolks and sugar with a hand mixer whitish thick (at least 10 minutes) , stir in the mascarpone, Grand Marnier and lemon juice. Beat whipping cream until stiff and fold in gently. Beat egg whites and sugar until stiff and fold in carefully to the mascarpone creame mixture.
6. Completion: Cut the cooled down pie crust base horizontally into three equal slices. Set the lowest of the three crust slices into the cleaned springform pan , drizzle with some espresso and some Grand Marnier. Spread 1/3 of the cream onto the bottom layer and smooth down.
7. Lay the second, middle disc onto the spread cream and proceed likewise the bottom part. Place the third top crust disc onto the second cream layer so that the cut surface facing up, soak with the remaining espresso and Grand Marnier and spread the remaining 1/3 mascarpone cream. Smooth down. Sprinkle thickly with the cocoa powder and let rest at least 5 hours in the refrigerator.
8. To serve: Separate Tiramisu from the edge of the springform pan using a knife. Open clip and remove the springform edge. Slip tiramisu onto a cake plate. Cut tiramisu into cake like pieces and serve on chilled plates.
Instead of Grand Marnier you can also take rum or amaretto.