Start by bringing a large pot of salted water to a boil for the potatoes—this takes time, so begin here. While the water heats, cook the bacon in a skillet over medium heat until crispy (about 8-10 minutes), then transfer to a paper towel-lined plate to cool and crumble. Place eggs in a separate pot, cover with cold water, bring to a boil, then remove from heat and let sit for 10 minutes before transferring to an ice bath to cool. Once cooled, peel and dice the eggs into 1/2-inch pieces. Dice the cheddar cheese into small cubes and slice the spring onions (both white and green parts), keeping them separate.

Add the 3.5 lb potatoes (cut into 1-inch cubes) to the boiling salted water and cook for 18-20 minutes, stirring occasionally, until a fork easily pierces the largest pieces but they still hold their shape—they should not be mushy or falling apart. Drain thoroughly in a colander and let sit for a few minutes to cool slightly before transferring to a large mixing bowl.

In a medium bowl, whisk together the mayonnaise, sour cream, Dijon mustard, and apple cider vinegar until smooth and well combined. Add the garlic powder, paprika, and a generous pinch of salt and black pepper, then taste and adjust seasonings to your preference. I always taste the dressing at this stage because it ensures the flavors are balanced before it's tossed with all the other ingredients—it's much harder to adjust once everything is mixed together.

To the warm potatoes from Step 2, add the crumbled bacon, diced eggs from Step 1, cheddar cheese cubes, and the white parts of the spring onions. Pour the dressing from Step 3 over the mixture and gently fold everything together with a rubber spatula until well coated, being careful not to break up the potatoes. Taste and adjust salt and pepper as needed. I like to let the salad sit at room temperature for about 10 minutes before serving so the flavors can meld together, but you can also chill it if you prefer—just bring it back to room temperature for the best flavor. Garnish with the reserved green spring onion tops just before serving to add a fresh, sharp note.