Cook the new potatoes in salted water until tender, 15 minutes max.
Boil the eggs for 10 minutes. Drain and shock under cold water.
Stew the green beans for 5 minutes. Drain and shock under cold water.
If desired, you can cook the potatoes, eggs and beans in 1 bowl at a time.
Fry the bacon strips in a pan without adding fat until crispy Drain on kitchen paper.
In the same pan melt a knob of butter and add the potatoes, cutting them into smaller pieces if desired. Let them get a crust and then add the beans and bacon.
In a bowl, mix the egg yolks, mustard and white wine vinegar. While stirring, add the olive oil and make a smooth dressing. Season to taste with salt and pepper.
Divide among the plates. Garnish with the red onion, dressing and halved hard-boiled eggs.