Gradually add the eggs that you've been with a whisk lightly beforehand. Once you've beaten everything well, add the flour with a pinch of salt and then the walnuts.
You're going to get a sticky mixture that you need to lay out in an oven dish with lightly greased baking paper. Bake in a preheated 356°F (180 °C) oven for 30 min. - it needs to remain juicy on the inside and have a crust on the outside.
For the cream, beat the yolks until whitened in a water bath. Make sure the bowl in which you're beating the yolks doesn't touch the water because the yolks may end up getting cooked.
Gradually add the sugar and remove from the heat. Beat the mascarpone with the rum or Marsala and add the yolks, while stirring nonstop.
Cut the baked layer into 2 separate layers that you will then stick together with generous amounts of cream. You can cut the cake into squares and serve with the cream, garnished with strawberry jam.
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