Wrap the potatoes and microwave at 600W for 4–6 minutes, or until tender. Carefully remove the skins once cool enough to handle.
Bring enough water to cover the eggs to a boil. Carefully lower in the eggs and cook for 6 minutes.
Transfer the eggs immediately to ice water and let them sit for 5–10 minutes, then peel.
Thinly slice the cucumber, sprinkle with a little salt, and let sit for about 5 minutes. Squeeze out the excess moisture.
Chop the bacon and cook in a skillet until crispy.
In a large bowl, mix the Greek yogurt, mayonnaise, mustard, milk, and black pepper.
Add the potatoes, 3 soft-boiled eggs, cucumber, and crispy bacon.
Gently smash the potatoes and eggs while folding everything together with the dressing.
Top with the remaining soft-boiled egg and extra black pepper, then serve.
