Combine lukewarm water, yeast, and sugar in a bowl. Stir lightly and let sit for 5 minutes until foamy.

Add flour, curry powder, baking powder, salt, sugar, and cooking oil to the same bowl. Mix until no dry flour remains, then cover and rest for 10 minutes. Place the dough bowl over warm water (about 113°F / 45°C) and allow it to rise for 30 minutes until slightly expanded.

Meanwhile, prepare the curry filling. Place the onion, garlic, and ginger in a food processor and pulse until very finely chopped. Heat the cooking oil in a pot over medium-low heat. Add the minced aromatics and cook for 5–6 minutes, stirring frequently, until golden and fragrant.

Add the ground meat and cook until fully browned. Stir in the Japanese(or non Japanese) curry powder and coat evenly. Add tomato paste, yogurt, water, sugar, soy sauce, salt, and chicken bouillon powder. Stir well to combine. Reduce heat to low and simmer uncovered for 10 minutes, stirring occasionally, until thick and concentrated.

Punch down the dough, knead for about 3 minutes, divide into 6 portions, shape into balls, and rest for 15 minutes.

Flatten each dough ball into about a 4-inch (10 cm) circle. Place cheese and curry filling in the center. Bring one pair of opposite edges together and pinch lightly. Bring the other pair together to form a diamond shape. Pinch the four seams closed, gather the corners at the top, and press the tip down slightly to seal.

Fill a steamer with water and bring it to a boil. Place the buns inside with the rounded side up, cover, turn off the heat, and let rest for 10 minutes.

Turn the heat back on. Once the water returns to a full boil, steam the buns for 12 minutes