You can chose any vegetables you like with this curry. Try to cut your root vegetables to roughly the same size and group vegetables into approx. cook times. So in this case, the carrot and sweet potato will take the longest so I add them to the sauce first, followed by the red capsicum, cauliflower, broccoli and lastly, I stir in the spinach to wilt. The cook time will depend on the size you have cut your vegetables. I like a fairly chunky curry, which is easier to cut up but takes a bit longer to cook than if you cut the vegetables smaller. Your call.
In a large, deep pan, melt the ghee, butter or coconut oil and sauté the onion, garlic, ginger and spices over a low heat unit the onion is just starting to become opaque and the spices smell amazing.
Transfer this to a blender or food processor with the cashews, tomatoes, sea salt, yoghurt and water and blend until it is smooth.
Add it back to the pan you cooked the onions and spices in (no need to wash it), add your vegetables in stages (see the note above), and simmer with the lid on (it will spit), stirring frequently until the vegetables are cooked to your liking. Taste and season again (salt is really important to bring the flavour of the spices out so make sure you season well).
My curry takes approx. 15 minutes for the root vegetables and another 5-10mintes for the quick cooking veggies (broccoli, cauliflower and capsicum). Always add leafy greens (baby spinach/coriander) at the very end once you have turned off the heat.
Another way to cook this curry is to steam (or roast) the vegetables and just mix through the sauce (which has simmered 10-15 minutes to build flavour).