Divide the cauliflower into large inflorescences and boil (I put it in boiling salted water, let it boil and after a minute I'm already throwing it into a colander, we like the cabbage to remain a little stiff). Let it cool down.
Cut the onion into half rings. Very small cucumbers should be cut in half lengthwise, larger cucumbers should be cut into four parts lengthwise.
Disassemble the cooled cabbage into small inflorescences.
Mix cabbage, onion and cucumbers in a convenient mixing bowl.
For dressing, mix vegetable oil and mustard with cereals. Mix it.