Mix the milk and vanilla sugar well and soak the brioche in it. It should soak in, but not be dripping with wetness.
Beat the eggs well with a whisk.
Toss the slices in it and fry in hot butter on both sides.
Immediately sprinkle with powdered sugar.
Arrange a dollop of “dulce de leche” on the plates and place the pain perdu on top. Serve the poor knights garnished with a scoop of vanilla ice cream and a few chocolate bars.