From the great cookbook, "Japanese Soul Cooking" by Tadashi Ono and Harris Salat. This is a great classic style Japanese curry that could also easily be made vegan with a few ingredient substitutions while remaining delicious.
Season the beef with salt and pepper
Melt 2 Tbsp. of butter in a large pot over medium heat
Cook the beef until browned evenly on all sides, about 2 minutes
Add onions and cook until translucent, stirring often, about another 5 minutes
Add the carrots, ginger, and garlic, cook for 2 more minutes
Add the apple, stock, and season with some more salt, reduce heat to low, cover the pot and simmer for an hour (in my experience you can reduce this time by quite a bit and it'll still be delicious if you're in a hurry)
While everything is simmering melt 4 Tbsp. of butter in a small saucepan
Add the flour and stir constantly for 3 minutes, until the butter takes on a light brown color and forms into small crumbs
Add the garam masala and curry powder and stir for two more minutes. Remove from the heat and set aside
After simmering the main pot, remove the lid and add the potatoes
Use a ladle to transfer one ladleful of liquid from the main pot to the pot containing the curry roux, and mix to form a paste
Transfer the roux paste from the small saucepan into the main curry pot, and stir well to combine
Simmer the curry for 20 minutes, or until the potatoes are cooked and tender
Serve with steamed white rice