Clean the cauliflower, cut out the hard stalk so that the head does not fall apart, and wash. In a large pot, boil up plenty of salted water with milk and 2 tablespoons of lemon juice.
Add the cauliflower (cabbage must be covered with water), weight down with a skimmer if necessary and cook for 15-17 minutes. Cut the crust off the toast. Cut the bread into pieces and grind finely in the universal chopper.
Roast bread crumbs in a pan without fat until golden brown, remove. Add butter and 1 tablespoon lemon juice to the pan, melt butter. Put the bread back in. Remove the cauliflower with a skimmer, drain well and arrange on a plate.
Froth butter once and sprinkle cabbage with it.