Pour 2 tablespoons oil into a large saucepan over medium-high heat.
Add potatoes and sauté for 3 to 4 minutes.
Reduce heat to medium, add cauliflower and continue to sauté for 4 to 5 minutes or until the potatoes and cauliflower begin to get soft and tender. Season with salt and pepper and 1 teaspoon curry powder.
Add green beans and continue to sauté for 2 to 3 minutes.
Remove from heat and transfer vegetables to a plate and set aside.
Place saucepan back over medium heat and add remaining oil.
Add onion to the pan and sauté for 3 to 4 minutes. Add garlic and ginger to the pan and continue to sauté for 2 to 3 minutes.
Stir in remaining curry powder, garam masala, coriander, and turmeric to pan and toast for 1 minute. Season with salt and pepper.
Transfer mixture to a blender and add cashews (with water) and half of the coconut milk.
Blend together until mixture is smooth.
Pour mixture back into the pan and simmer over medium-low heat. Stir in tomato paste and coconut milk and simmer for 5 to 7 minutes. Season with salt and pepper.
Stir sautéed vegetables and peas back into the sauce and simmer until vegetables are cooked through completely.
Adjust seasonings, if needed, and serve over brown rice or with flatbread.