Make the Preferment: Mix flour, water, and yeast in a small bowl. Cover and let sit at room temp for 6–12 hours (overnight is best) until bubbly.
Make the Dough: In a large bowl or mixer, combine the preferment, flour, yeast, salt, sugar, milk, and olive oil. Mix until a shaggy dough forms. Knead by hand (10–12 mins) or with dough hook (8–10 mins) until smooth, elastic, and slightly tacky.
First Rise: Transfer dough to a lightly oiled bowl. Cover and let rise until doubled, about 1–1.5 hours.
Shape the Loaf: Punch down dough, divide into 3 equal parts, and roll each into a rope. Braid the ropes and pinch ends to seal. Transfer to a parchment-lined baking sheet.
Second Rise: Cover and let the braided loaf rise until puffy (about 45–60 mins).
Preheat oven to 375°F (190°C).
Add Toppings & Bake: Brush loaf with egg wash, then generously sprinkle with sesame seeds. Bake for 25–30 minutes, or until deeply golden and hollow-sounding when tapped.
Cool: Transfer to a wire rack. Let cool at least 1 hour before slicing for best texture