Separate the yolks and whites from the eggs for the layer. Heat the oven to 356°F (180 °C). For the layer, whip the yolks and add the sugar, whipping well again. Pour in the flour and homogenize.
Separately, beat the egg whites into snow with a pinch of salt, then carefully mix into the other mixture. Transfer it to an oven dish with baking paper and bake 15 min. in a moderate oven - keep an eye on the layer to make sure it doesn't burn.
Take out the baked layer from the oven and put it on top of a moist towel right away, then wrap it into a roll with it.
For the filling, beat the ricotta with the pistachios and add the sugar, stirring well. Unroll the layer and smear it with this prepared cream.
For the chocolate cream, beat the egg well with the sugar, then mix with the corn starch and milk. Heat the entire mixture on a low stove.
Separately, melt the white chocolate in a water bath with 1 tbsp water, then add it to the warm cream. Pour this cream over the roll and let it set before serving.