On the following day, remove the pre-ferment from the refrigerator and preheat your oven to a temperature of 180°C. Proceed to soak the raisins in rum.
Using a food processor, blend together the butter, egg yolk, vanilla extract, lemon zest, and dry ingredients (flour, sugar, salt). Then, divide the pre-ferment into small portions and gradually add them to the mixture. Stir until a consistent dough is formed and it no longer sticks to the sides of the bowl. Lastly, incorporate the soaked raisins. Take the dough out onto a work surface, knead it by hand for several minutes, mold it into a ball, and allow it to rest.
While the dough is resting, use a food processor to beat the sugar, honey, butter, and ground walnuts until they are creamy. If the mixture appears too dry, you may add some milk to it.
Divide the dough into three equal parts. Proceed to roll out each part thinly on baking paper dusted with flour. Spread a third of the filling on each rolled-out piece of dough, then roll it up in the form of a roulade. Using a sharp knife, make vertical cuts at even intervals in the rolled-up dough until you reach the middle.
Grease a cake tin with butter and dust it with flour. Carefully braid the three filled, cut rolls, and place them in the tin. Cover them and let them rise for one hour at room temperature. Brush the top with egg white and bake it in the preheated oven at 180°C for 45 minutes, or until it turns golden brown. After baking, let it cool and sprinkle it with icing sugar before serving.