To make the tiramisu, beat egg yolks and caster sugar in an electric mixer on medium-high speed for 10 minutes or until it changes from yellow to pale yellow and is a thick consistency. Add vanilla and mascarpone and beat until just combined and smooth. Set aside.
Beat egg whites until stiff and foamy. Add half the mascarpone mixture into the egg whites. Gently fold through. When mostly incorporated, add the remaining mascarpone mixture and fold through until just combined.
To make the walnut praline, line a board with baking paper. Put the sugar in a small non-stick frying pan and shake the pan so the sugar spreads out evenly. Place the pan over a medium heat and cook the sugar undisturbed for about 2 minutes, until the edges start to melt. Shake the pan to redistribute the sugar and cook for a further 1-2 minutes or until the sugar has melted and caramelised. It can be gently stirred at this stage. Once all the sugar has caramelised, add the walnuts and quickly toss to coat in the caramel. Immediately tip onto the baking paper and spread out with a spoon. Put aside to set. Once set, chop the praline into small chunks.
To serve, dust with cocoa powder then scatter over the walnut praline, not long before serving.
* Or make your own dulce de leche Stove Top Dulce de Leche
* Or 100g dark/semi-sweet cooking chocolate, grated
Can be made a day ahead or can be frozen but leave off the praline until serving.
To freeze, line serving dish with plastic wrap before assembling the tiramisu, then once frozen it can be pulled out and wrapped. When ready to use, remove from freezer, immediately peel off plastic wrap and place back into the dish to thaw. (That way you don't have your dish occupied in the freezer!)
Praline can be made a few days ahead and kept in airtight container in fridge.
