Steps

1. Warm the milk, add 2 tbsp instant dry yeast, and mix.
   🕒 05:58
2. In a bowl, combine 300g bread flour, 1 tbsp sugar, 1 tsp salt, and 4g bamboo charcoal powder.
   🕒 06:17
3. Gradually add the activated dry yeast mixture and the remaining milk in 2-3 portions, mixing each time.
   🕒 06:38
4. Once the dough comes together, remove it from the bowl and knead until smooth on the surface.
   🕒 07:30
5. Add 10g butter, softened to room temperature, and knead it into the dough.
   🕒 08:02
6. When the dough becomes smooth and elastic, shape it into a ball, return it to the bowl, cover with plastic wrap, and let it proof in a warm place for 1 hour (first proofing).
   🕒 08:28
7. The dough should have doubled or tripled in size. Confirm the first proofing is complete by gently poking it with a finger.
   🕒 08:52
8. Remove the dough, gently press it to deflate, and divide it into 4 equal portions, shaping each into a ball.
   🕒 09:26
9. Place the dough balls on a baking sheet lined with parchment paper. Cover with a wrung-out damp cloth and let rest for 15 minutes.
   🕒 10:04
10. Gently deflate the dough again, reshape into balls, cover with the cloth, and let proof in a warm place for 30 minutes (second proofing).
    🕒 10:13
11. Preheat oven to 190°C (375°F).
    🕒 11:02
12. After placing the buns in the oven, reduce the temperature to 140°C (285°F) and bake for about 20 minutes. (Key Tip!) Lowering the oven temperature when baking helps maintain the beautiful black color while ensuring the buns remain fluffy and soft.
    🕒 11:10
13. Let the baked buns cool to room temperature.
    🕒 12:13
14. Heat vegetable oil in a frying pan. Grill the 2 onion slices until golden brown on both sides and set aside.
    🕒 11:23
15. In a bowl, thoroughly mix 300g mixed ground meat, 3 tbsp milk, 3 tbsp breadcrumbs, 1 tbsp all-purpose flour, 1/3 tsp salt, and 1/3 tsp curry powder. (Key Tip!) Omitting eggs creates a meatier burger. Curry powder helps eliminate any gamey smell from the meat.
    🕒 12:45
16. Knead the mixture vigorously until it becomes fluffy, ensuring the lean meat and fat are well combined. (Key Tip!) The ideal consistency is when the mixture resembles Darth Maul's head.
    🕒 13:30
17. Divide the kneaded mixture into 2 equal portions. Gently shape them into flat, round patties, removing any air bubbles. (Key Tip!) Make the patties slightly larger than desired to account for shrinkage during cooking.
    🕒 13:55
18. Add more vegetable oil to the same frying pan and heat. Place the shaped patties and grill until golden brown on both sides, then set aside.
    🕒 14:17
19. Slice the cooled buns in half horizontally. (Key Tip!) Cutting the top bun slightly larger than the bottom will improve presentation. The buns are soft, so cut slowly without pressing down too hard.
    🕒 14:47
20. Lightly spread the [A] mayonnaise-mustard mixture (1 tbsp mayonnaise, 1/2 tsp French mustard) on the cut sides of the buns.
    🕒 15:41
21. Place 2 lettuce leaves on the bottom bun. (Key Tip!) Lettuce prevents moisture from the buns becoming soggy.
    🕒 16:03
22. Layer the grilled onion slices, tomato slices, grilled patties, and 2 slices of cheese in that order.
    🕒 16:34
23. Drizzle ketchup and Otafuku Sauce (Okonomiyaki Sauce) over the toppings, then place the top bun to complete the burger.
    🕒 17:26
24. Cut the purple sweet potato into thick sticks.
    🕒 19:05
25. Deep-fry the cut purple sweet potato in medium-hot oil until golden brown, then sprinkle with salt.
    🕒 19:05
26. Mix a small amount of blue food coloring into milk to create blue milk.
    🕒 19:15