Okroshka

Ingredients

• 1 large Yukon Gold potato, cut into a 1/3-inch dice
• 6 large hard-boiled eggs, divided
• 1/4 cups Dijon mustard
• 1 cup smetana or European-style sour cream
• 1 quart plain kefir
• 1 cup water
• 1 pinch kosher salt, plus more to taste
• 1/4 pounds hot-smoked, salo (pork belly) or ham, cut into a 1/3-inch dice
• 1 bunch radishes, cut into a 1/3-inch dice
• 2 pickling cucumbers, peeled and cut into a 1/3-inch dice
• 1/2 cups sliced scallions (reserve some for garnish)
• 1/2 cups finely minced dill (reserve some for garnish)
• 1 pinch freshly ground black pepper, plus more to taste