Wash the potatoes and cut them into thick slices.
Place the potatoes in a bowl of cold water as you are slicing them to prevent discoloration.
Boil the potato slices in a large pot of water for 15 to 20 minutes, until tender but firm.
While the potatoes are boiling, make the dressing by placing the mustard, vinegar, olive oil, salt, pepper, 1 tablespoon of dill, garlic, and 1 tablespoon of chives in a small bowl and whisking together.
Drain the potatoes in a colander, run cold water over them quickly, and then let them dry for a few minutes.
Place the potatoes in a large bowl, drizzle about a third of the dressing, and gently toss to coat. Set aside.
I like to use fresh raw peapods, but if the peas and pods are too fibrous or tough, blanch them in boiling water for a few minutes, then run cold water over them and dry them on paper towels before proceeding.
Prepare the peapods by either slicing them on the diagonal and adding them to the potatoes or, as I did in the photos, running a sharp knife across the top of each pod, pulling the two halves apart. Slice the side of the pod the peas didn't stick to. Set aside the pod halves with the peas attached to them.
Toss the peapods with the potatoes.
Garnish with dill sprigs, the remaining chives, and the peapods with the peas still attached.
Serve with remaining dressing.