Knead a dough from 500g of flour, 1 egg, 1 tablespoon of sugar, 2 tablespoons of oil, 1 teaspoon of salt, and a cup of milk with 15–20g of yeast dissolved in it. Place the dough in a deep bowl of room-temperature water and let it sit until it rises to the surface. When it floats, remove the dough from the water, add a little more flour, knead the dough lightly, and divide it into balls the size of a chicken egg. Let the balls rise slightly, brush them with egg yolk, and bake them in a moderately hot oven.
Once baked, cut off the tops of the balls and scoop out the insides with a spoon. Fill the shells with Olivier salad, crumbled feta cheese, or any other filling you prefer, and garnish with diced boiled or pickled beets, diced carrots, chopped boiled egg whites, and chopped parsley. Make handles from the same dough or cut them from lemon peel and attach them to the baskets.
