Dissolve the sugar and yeast into the warmed milk, cover, and put aside for 10 minutes.: The warm milk should feel like a cozy bath, not hot to the touch, and as the sugar and yeast mingle you will notice a light foam forming after several minutes, a sign of a lively yeast . This scent of faint fermentation is reassuring and signals that fermentation is starting to produce tiny gas bubbles that will lift the dough. If you do not see any foaming, your yeast may be old or the milk was too hot, so try again with fresh yeast or cooler liquid. Avoid adding cold milk because the yeast will not wake up well and the rise will be sluggish.
Put the flour, salt, melted butter, 1 egg, and 1 egg yolk in a large bowl, mix, and pour in the activated yeast mixture.: After combining these enriched elements, the dough will start to come together into a slightly sticky mass. Use your hands or a sturdy spoon to bring the ingredients into a shaggy dough before kneading so the fats and proteins begin to unite; you will smell a warm, bready aroma as the emulsion forms. If the dough feels excessively dry, a tablespoon of warm milk helps, whereas too wet a dough can be corrected with a dusting of flour . Be careful not to add too much flour at once, that can toughen the loaf.
Knead the dough for 10-15 minutes, cover, and leave to rise for about 1 hour in a warm place until it doubles in size.: Proper kneading develops gluten so the dough becomes smooth and slightly elastic, which you will notice under your palms as it stretches and springs back. The texture will change from shaggy to satin smooth, and when you press an indentation it should slowly fill back in. During the rise the air pockets formed by the yeast will give a gentle yeasty aroma. If the dough does not rise well, the room may be too cool, so find a slightly warmer spot or allow more time. Avoid punching it down aggressively at this point, as you want to preserve those delicate air bubbles.
Place the dough on a floured surface and divide into 6 equal parts. Roll each part into a ball, cover, and leave to rise for 10 minutes. Then roll the dough balls into sticks.: Working on a floured board, feel each piece transform from a ball into a smooth rope, the surface tightening as you roll. After the short bench rest the gluten relaxes, making the shaping easier and preventing spring back. The ropes should be uniform in thickness so the braid bakes evenly and you will notice the strands hold tension without tearing. If the dough resists rolling, give it another minute to relax under the cloth, forcing it usually leads to irregular strands.
Take 3 rolled sticks and braid them, joining the ends. Do the same for the other 3.: Braiding is tactile therapy, and the interlaced strands will press together, creating that classic plaited look. Keep an even, gentle tension so the braid is snug but not constricted, which helps the loaf expand uniformly in the oven. If one strand is thicker, adjust by gently stretching or compressing to match the others; unequal strands will create uneven baking and different textures in the finished loaf. Don’t rush the braid, steady hands make a neat, attractive loaf.
Place them gently on baking paper, beat the remaining egg and brush over the top. Let it rest for 30 minutes while you preheat the oven to 356° F/ 180 °C.: The glossy egg wash will amplify browning and give a lacquered sheen. As the braid rests, you will see it puff slightly and the egg will settle into crevices, readying the surface for an even golden finish. The room will fill with a faint sweet yeast scent as the final rise completes. If the wash pools in low spots, dab lightly with a brush to avoid overbrowning. Ensure your oven is fully heated to 356° F/180 °C so the loaf begins browning immediately upon baking.
Bake at 356° F/180 °C for 35-45 minutes. Let them cool before serving.: During baking the crust will gradually darken to a deep golden brown while the interior sets into a tender crumb, and you may notice a pleasant, toasty aroma filling the kitchen. A properly baked loaf should sound hollow if lightly tapped on the bottom, and an instant read thermometer placed into the center will register a warm, set interior. If the top browns too quickly, tent with foil to prevent overbrowning while the center finishes baking. Allow the loaf to cool thoroughly so the crumb firms and slices cleanly.