Prepare Dough: In a large mixing bowl, combine bread flour, cake flour, and salt. In a separate bowl, whisk together warm milk, melted butter, sugar, and instant yeast. Mix wet into dry, add egg, and stir until shaggy. Transfer to floured surface.

Knead Dough: Knead by hand for 10-12 minutes or with a stand mixer for 8-10 minutes until smooth and elastic. Place in oiled bowl, cover, and let rise until doubled, about 60-90 minutes.

Make Filling: Heat oil in a pan over medium heat. Sauté onions, carrots, and potatoes for 5-7 minutes. Add ground beef until browned. Stir in soy sauce, ketchup, and curry roux. Add water and cornstarch as needed and cool.

Assemble Bread: Punch down the dough and divide into 16 pieces. Flatten each into a disk, add filling, pinch edges to seal.

Coat and Fry: Whisk egg in one bowl and place breadcrumbs in another. Coat each bread in egg then breadcrumbs. Heat oil in fryer to 350°F (175°C). Fry for 4-5 minutes until golden brown.

Drain and Serve: Remove from oil and drain on paper towels. Cool slightly and serve warm with dipping sauce or pickled vegetables.