Mix vinegar and mustard. Season with salt. Gradually fold in 3 tablespoons of olive oil. Wash the thyme, dab dry (put some twigs aside for garnishing) and pluck the leaves from the stalks. Chop the thyme finely and stir into the vinaigrette.
Clean, wash and spin-dry frisée and romaine lettuce. Halve romaine lettuce leaves diagonally. Wash, dab dry, clean and slice the tomatoes. Cut baguette into narrow slices. Heat 3 tablespoons of olive oil in a pan and fry the baguette slices until golden brown. Season with salt. Peel onions and cut them into thin slices. Halve the avocados and remove the stone. Peel the flesh and cut into slices.
Season with salt. Peel onions and cut them into thin slices. Halve the avocados and remove the stone. Peel the flesh and cut into slices. Arrange lettuce, tomatoes, onions, baguette slices and avocado slices together and sprinkle with vinaigrette. Sprinkle with black pepper and garnish with thyme