Boil the potatoes and beets (if not using pre-cooked beetroot) until fork-tender. In a medium pot, add the potatoes and enough water to cover the potatoes by 2 inches or so. Over high heat, bring to a boil. Once boiling, turn the heat to medium, and boil the potatoes for about 25 minutes. In a separate pot, you can boil the beets using the same process, but it will take 45-60 minutes, depending on the size of the beets.

Next, make hard-boiled eggs. In a medium pot, add the eggs and enough water to cover the eggs by 1-2 inches or so. Over high heat, bring to a boil. Once boiling, turn the heat to medium, and boil for 5 minutes. After 5 minutes, turn the heat off, and let them sit in the hot water for another 5 minutes (cover the pot with a lid). Then, transfer them to a bowl with ice-cold water. Afterward, when they’re cool enough to handle, peel the eggs.

Peel the potatoes, beets, and apple. Then, dice the potatoes, beets, pickles, apple, and herring. Add them all to a bowl.

In a separate bowl, mix the mayo, mustard, horseradish, sour cream, and salt.

Add the mayo mixture to the bowl of vegetables and mix it well. Once mixed, place it in the fridge for 20-30 minutes.

Now chilled, your rosolje is ready to be served! Plate the salad, and top it with the halved hard-boiled eggs and parsley (optional), and get ready to dive in!