Peel the asparagus and cut off the woody ends. Cut the asparagus into very thin pieces. Peel and halve the onions and cut them into strips. Wash the liver and pat dry. Cut them into thin, diagonal pieces, season with salt and turn them in the flour.
Clean and wash the pointed cabbage and cut into very thin slices. Pluck the thyme leaves from the stalks. Season vinegar and lemon juice with salt, pepper and sugar. Whip the oil into it. Fry the cabbage, asparagus and onion strips in 2 tablespoons of hot fat. Deglaze with 1/4 litre water, cover and steam for about 5 minutes. Meanwhile fry liver in remaining hot fat while turning for about 3 minutes and cut into strips. Arrange on plates sprinkled with thyme. Sprinkle with the vinaigrette.
Fry the cabbage, asparagus and onion strips in 2 tablespoons of hot fat. Deglaze with 1/4 litre water, cover and steam for about 5 minutes. Meanwhile fry liver in remaining hot fat while turning for about 3 minutes and cut into strips. Arrange on plates sprinkled with thyme. Sprinkle with the vinaigrette. Serve garnished with lemon