Heat the butter in a small saucepan over medium heat. Once melted, add the flour and reduce the heat slightly. Stir until combined, then reduce the heat to low and cook until the mixture reaches a dark chocolate color (about 15 minutes).

Add the curry powder to the roux and stir to combine. Then add the garam masala and, optionally, cayenne. Stir and cook for 20 to 30 seconds, then transfer to a bowl and set aside.

Preheat a large pot over medium heat. Add the olive oil, onion, potatoes, squash, and carrot to the pot. Toss the vegetables to coat them with oil, then add the grated ginger and mix. Cover with a lid and reduce the heat to low so the vegetables can steam for 15-20 minutes, until mostly cooked. Periodically shake the pot or remove the lid and stir to keep the vegetables from burning.

Heat a large frying pan over medium heat. Add the olive oil and eggplant. Fry until browned (8-10 minutes) and then transfer them to a plate.

Wipe the pan clean and add the last tablespoon of oil. Then add bell pepper and asparagus and saute until slightly tender. Season with salt and pepper, then transfer them to the plate with the eggplant.

Add the butter to the pan, then add all of the mushrooms and saute for about 4 minutes. Season with salt and pepper, then transfer to the plate. By this point, the hard vegetables in the pot should be ready.

Once the hard vegetables are about 80% done, add the vegetable broth and bay leaf. Bring to a boil over medium-high heat, then skim any scum and cook until the vegetables are done all the way through. Turn off the heat and add the sauteed vegetables (reserving some to put on top when serving later) and mushrooms to the pot.

Use a ladle to get some of the hot broth. Add some of the roux to the ladle, stir until completely dissolved, then add back to the rest of the curry. Taste the sauce and repeat until it reaches the desired flavor and consistency. Bring back to a simmer and add grated apple bit by bit, tasting along the way, for sweetness. Season with salt to taste. Serve with white rice and add any reserved vegetables back on top.