Cut the potatoes into chunks about 2 inches in size (no need to peel—the skin adds texture and nutrients). Place them in a large pot of cold salted water and bring to a boil over high heat. While the water heats, finely dice the onion into 1/4-inch pieces and mince the garlic cloves. Remove the dill stems and finely chop the leaves. Have all ingredients measured and ready before the potatoes finish cooking, as the timing from here moves quickly.

Once boiling, reduce heat to medium and simmer the potatoes for 15-18 minutes until a fork easily pierces the largest piece—you want them tender but not falling apart. While they cook, whisk together the mayonnaise, Dijon mustard, olive oil, lemon juice, and sugar in a large bowl until smooth and well combined. Fold in the diced onion, minced garlic, and chopped dill. Season generously with salt and freshly ground black pepper, tasting as you go. I like to add the dressing components separately rather than all at once so I can taste and adjust the seasoning before the potatoes go in.

Drain the cooked potatoes in a colander and let them sit for just 1-2 minutes to allow excess moisture to evaporate. While still warm (this is important—warm potatoes absorb flavors better than cold ones), transfer them to the bowl with the dressing. Gently fold everything together until the potatoes are evenly coated, being careful not to break them apart. Taste and adjust seasoning with additional salt, pepper, or lemon juice if needed.

Transfer the potato salad to a serving bowl and refrigerate for at least 1 hour before serving. This allows the flavors to meld together and creates that classic creamy texture. I find the salad tastes even better if made a few hours ahead or the day before—the potatoes continue to absorb the dressing and become more flavorful.