Mince the garlic cloves finely and chop the fresh dill. Slice the scallions into thin rounds, keeping white and green parts separate if you prefer. Measure out the corn kernels (if using fresh corn, cut from the cob now). This prep work ensures you're ready to move quickly once the potatoes are cooked, which is crucial since potatoes absorb dressing best while still warm.

Cut the potatoes into 1/4-inch slices—I like to leave the skin on Yukon Golds for texture and nutrients. Bring a large pot of salted water to a boil, then add the potato slices and cook for 10-13 minutes until they're tender but not falling apart. You want them soft enough to absorb dressing but still holding their shape. Drain and rinse briefly with cold water to stop the cooking process, then transfer to a large mixing bowl.

In a small bowl, whisk together the stone ground mustard, minced garlic from Step 1, salt, black pepper, and both the rice wine vinegar and apple cider vinegar. Let this mixture sit for a minute to allow the garlic to infuse the dressing. Then slowly whisk in the olive oil until emulsified. The emulsification helps the dressing coat the potatoes evenly and creates a silkier texture.

While the potatoes from Step 2 are still warm, season them with salt, black pepper, and the additional 1.5 tbsp apple cider vinegar. Toss gently to coat. Warm potatoes absorb vinegar and flavors much better than cold ones, which is why we dress them immediately. Pour the vinaigrette from Step 3 over the potatoes and toss everything together until evenly coated.

Gently fold in the corn kernels, sliced scallions, and chopped dill from Step 1. I like to add the dill last so it stays bright and vibrant rather than getting bruised or wilted. Toss everything together gently but thoroughly, being careful not to break up the potatoes. Taste the salad and adjust seasoning with additional salt and pepper as needed.

Transfer the potato salad to a serving dish and refrigerate for at least 1 hour before serving. This allows the flavors to meld together and the salad to set. The cold temperature also brings out the fresh, bright flavors of the herbs and vinaigrette. Stir gently before serving to redistribute any dressing that may have settled to the bottom.