Peel the potatoes and cut them into 1 inch cubes. Keep the cubes close in size so they cook evenly and become tender at the same pace.

Bring a large pot of water to a rolling boil, season it with salt and a splash of oil, then cook the potatoes for 5 minutes before adding the elbow macaroni. Continue boiling until the potatoes yield easily to a fork and the macaroni is tender and plump.

Drain the potatoes and macaroni well, then immediately toss them with the apple cider vinegar. The warm starches should take on the vinegar’s bright aroma without looking wet or soupy.

Whisk the mayonnaise, milk, sugar, salt, and pepper together in a large mixing bowl. The dressing should look smooth and pourable, with no streaks of milk remaining.

Add the warm potato and macaroni mixture to the dressing and stir until coated. Each noodle and potato cube should have a creamy sheen.

Fold in the grated carrot, grated onion, and roughly chopped hard boiled eggs. Use a gentle motion so the potatoes stay in pieces and the eggs remain pleasantly chunky.

Cover the bowl and refrigerate the salad for 4 hours or overnight. The dressing will thicken as it chills and the flavors will settle into the pasta and potatoes.

Serve the salad cold. Stir gently before serving and look for a smooth, glossy coating throughout.