While the spinach Is cooking, cook the eggs hard.
Cut eggs in halves crosswise and remove the yolks.
Cut a slice from the bottom of each cooked egg white so that it will stand on a platter.
Season the yolks with red pepper, mustard, butter and salt.
Mix thoroughly with vinegar to taste.
Fill the egg cups with the spinach, mounding it high, and put the rest around the egg.
Put the prepared yolks in a ricer and squeeze over all.