Divide the cauliflower into large inflorescences and boil (I put it in boiling, salted water, let it boil and in a minute it was thrown into a colander, we like the cabbage to remain a little hard). Allow to cool.
Cut the onion into half rings. Very small cucumbers cut in half lengthwise, larger ones-lengthwise into four parts.
Parse the cooled cabbage into small inflorescences.
Combine the cabbage, onions and cucumbers in a convenient mixing bowl.
For the dressing, mix the vegetable oil and mustard with the grains. Stir.