Pour the milk and water into a small saucepan and heat gently until warm, not hot.Pour the warm liquid over the yeast, add the sugar, and mix well until dissolved.Let the mixture rest in a warm place for about 15 minutes, until the yeast starts to foam.
Sift the flour into a large mixing bowl, then add the salt and the activated yeast mixture.Pour in the warm milk-and-water mixture and knead for 15–20 minutes, until the dough starts to come together and becomes elastic.
Gradually add the oil in 2–3 additions, kneading well after each addition. Continue kneading for another 20–30 minutes, until the dough is smooth, soft and slightly glossy.
For a soft and fluffy festive bread, the dough needs to be kneaded as thoroughly as possible. Once you finish kneading, transfer the dough to a lightly oiled bowl and brush the top of the dough with a thin layer of oil. Cover the bowl with plastic wrap or a clean kitchen towel and let it rise in a warm place for 40–60 minutes, until doubled in size.
Prepare your work surface by greasing it with a little oil, then gently turn the risen dough out of the bowl.Divide the dough into 3 equal pieces and shape each piece into a ball.Roll each ball into a long rope of the same thickness, ready for braiding.
Place the 3 ropes parallel to each other on the work surface and pinch the ends together firmly at one side so they do not come apart while braiding.
Braid the ropes into a simple three-strand braid, like a hair braid: move the right strand over the center, then the left strand over the new center, repeating until you reach the end.
Pinch the ends together at the other side as well, then bring the braided dough around to form a ring. Join the two ends to form a wreath and tuck the seam underneath so it is hidden.
Transfer the wreath to a baking tray lined with parchment paper and let it rise for another 20–30 minutes. Brush the top with egg yolk mixed with a little milk or water, sprinkle generously with sesame seeds, and bake at 350°F (180°C) until deeply golden and well baked through.