Brown the beef: Heat a large skillet over medium heat. Add minced garlic and cook for 1 minute until fragrant. Add ground beef and brown for 4 minutes. Season with salt and black pepper. Remove from the skillet and set aside.
Sauté the onions: In the same skillet, add diced onions and cook until softened and lightly golden, about 2 minutes.
Add curry cube: Stir in the Japanese curry cube with the onions and cook until melted. Add ground beef back into the pan.
Make curry sauce: Add dashi powder and garlic powder, and pour in milk. Stir until the sauce becomes rich and smooth. Stir in ketchup for extra sweetness.
Adjust thickness: Let sauce simmer for 3-4 minutes until desired thickness. If you prefer a thinner consistency, add 2 tbsp of water and adjust.
Serve and garnish: Spoon the curry over a bed of steamed rice and top with bonito flakes for a smoky, umami-packed finish. Enjoy!