In stand mixer fitted with a paddle attachment, add 1 cup flour, yeast, sugar and salt to bowl; mix well. In saucepan or microwave-safe dish, heat milk, water and butter to 120-130°F (butter does not need to melt). Add to flour mixture. Blend on low speed for 30 seconds; beat on medium speed for 4 minutes. Add eggs; beat 1 minute.
Switch to dough hook attachment. Gradually stir in enough remaining flour to make a firm dough. Knead until smooth and elastic, about 5 to 7 minutes.(NOTE: For hand mixing: following above steps, mix ingredients in large mixing bowl using a wooden spoon or dough whisk. Knead on floured surface until smooth and elastic.) Place dough in lightly oiled bowl and turn to grease top. Cover; let rise until indentation remains after poking dough with finger down to second knuckle, about 1 hour.
Punch down dough; turn out onto a lightly floured surface.
To Braid: Divide dough into 3 equal parts. Roll each section to form a rope about 1-inch in diameter. On greased cookie sheet, braid ropes; pinch ends to seal and tuck under ends. Cover; let rise in warm place until indentation remains after touching, about 40 minutes.
Preheat oven to 375°F.
Brush egg wash on risen dough. Sprinkle with sesame or poppy seed, if desired. Bake at for 30 to 35 minutes. Remove from cookie sheet; cool on rack.