Place all-purpose flour in a bowl then sprinkle yeast on top. Using a pair of chopsticks, slowly add the water while stirring the flour until there are no dry spots of flour left in the bowl. Then, switch to your hand and knead into a soft dough. Cover with a moist towel and place a lid over. Let it proof until 1.5X than its original size, about 30-35 minutes.
While waiting, make the oil paste. Add flour to a bowl and heat the oil. (To test the oil readiness, stick a chopstick into the oil, once you see bubble forms around the tip of the stick, it's ready).
Carefully pour the hot oil into the bowl with flour. Stir to combine into a paste and let it cool slightly.
Preheat the oven to 475F°F (245°C).
Next, dust the work surface with flour. Uncover the bowl and transfer the dough over. Roll it out into a large rectangle aiming for 3mm thickness. Mine came out to a 16"X10" rectangle.
Spread ⅔ of the oil paste over and place the chopped onions in the middle of the dough. Gently press green onions to adhere (see video or pictures above).
Lift up the bottom layer and flip over to cover the green onions. Then, spread the remaining oil paste and green onions on top. Bring the top part over to cover and then pinch to seal all the openings. Flip it over so the seamed side is facing down.
Now, whisk together maple syrup and milk together until incorporated. Brush the dough with a layer of wash. Then, pack the top with sesame seeds.
Cut into 6 equal portions (I used a serrated knife).
Transfer to a baking tray, 1-inch apart.
Bake for 12 minutes until golden brown. (Fully baked bread will have a hollow sound when you tap on it. The inside should be fully cooked through as well). Serve hot as-is or cut it open and stuff with your favorite filling.