Mix the flour with the baking powder and salt. Stir the butter with the sugar until foamy white, and gradually stir in the eggs. Add the flour mixture and the milk to the batter, stirring until the batter tears heavily when it falls from the spoon.
Grease a wreath-shaped cake pan, and scatter it with breadcrumbs. Pour the batter into the pan, spreading out until it is somewhat smooth.
Bake for about 45 minutes. Remove the cake from the pan. Allow the cake to cool and then cut it twice horizontally, into three even layers.
For the filling: mix the pudding powder with 3 tablespoons of milk. Bring the remaining milk, the sugar, butter and salt to a boil. Remove the pan from the stove and stir in the pudding powder mixture. Bring to a boil while stirring.
Separate the egg, mix the yolk with a little of the hot pudding and stir in the remaining pudding. Beat the egg whites until stiff and fold in. Allow filling to cool slightly.
Brush the bottom cake layer with 1/3 of the filling, add the middle layer and spread with the second third of the filling. Place the last layer on top and press down.
Use the remaining vanilla filling as frosting for the cake. Sprinkle with the crushed brittle. Set the cake aside to allow the filling to soak in slightly.