Dice pretzel sticks. Melt the butter in a large pan, toast the cubes over low heat while turning and remove.
Cut the onions into fine rings, dice the cucumber, cut the radishes into thin slices. Cut the meat loaf into strips, finely chop the parsley.
For the vinaigrette, mix together vinegar, mustard, salt, pepper and sugar and beat in grapeseed oil. Mix the meat loaf, onions, cucumber, radishes, parsley and vinaigrette. Let it steep for about 30 minutes. Sprinkle with a few pretzel croutons in a salad bowl. The remaining croutons are enough.