Tear up and bake the phyllo pastry until golden. In the meantime, prepare the cream by heating the milk and sugar on the stove and put some of the milk aside for the flour.
When the milk begins to boil, pour the dissolved flour with milk that you set aside in a thin trickle, stirring vigorously to thicken the cream. Leave it to cool and add the butter and vanilla ( or lemon zest ) and mix until it absorbs the butter (the cream must not be hot when you add the butter because it will harden and run).
Stir the confectionery cream and mix it gradually with the cooled cream. The cream will become fluffy. Begin to assemble the cake. In a cake mold with removable walls, lay out some baking paper, put a layer of baked phyllo pastry at the bottom, then a layer of cream.
Repeat until you run out of the ingredients, leave it to harden in the fridge. Then slide a knife along the walls, if you need to separate the cake from them.
Decorate it as desired.