First grease a springform pan (26 cm diameter) with butter.
Sift the flour into a bowl, dissolve the yeast in the lukewarm milk and add to the flour with the salt and sugar. Add the egg and butter and knead well. Cover the dough with a kitchen towel and let it rise in a warm place for about 1 hour.
In the meantime, prepare the cream filling. To do this, mix the egg yolks with the sugar in a bowl until foamy, add the flour, dilute with a dash of milk and bring the remaining milk to the boil in a saucepan.
While stirring constantly, add the egg yolk mixture and continue stirring for about 4 minutes while simmering. Then allow to cool while stirring.
Dust the work surface with a little flour and roll out the dough into a rectangle 1/2 cm thick.
Spread the cream filling on it, roll up the dough and cut it into 6 pieces of about 7 cm.
Place the dough snails in the prepared springform pan and let the dough rise for about 1 hour.
Preheat the oven to 200 °C and brush the dough in the springform pan with beaten egg yolk.
Bake for about 45 minutes at 200 °C in the oven until golden brown, let cool well.
Brush the chinois with the powdered sugar glaze and let dry.