Sauté Aromatics: In a large pot or deep skillet, heat the oil or ghee over medium heat. Add the finely chopped onion and cook for 5-7 minutes, until soft and translucent. Add the minced garlic and grated ginger and cook for another minute until fragrant.

Toast the Spices: Reduce the heat to low. Add the curry powder, cumin, coriander, and turmeric to the pot. Stir constantly and cook for about 30 seconds to 1 minute, until the spices are fragrant. This step is crucial for unlocking their full flavor.

Add Tomatoes and Liquid: Pour in the crushed tomatoes and stir well, scraping up any spices from the bottom of the pot. Stir in the coconut milk and vegetable broth. Bring the mixture to a gentle simmer.

Simmer and Season: Reduce the heat to low and let the curry sauce simmer for at least 15-20 minutes, stirring occasionally. This allows the flavors to meld together and the sauce to thicken. Season with salt and pepper to taste.

Serve: The curry sauce is now ready. You can add cooked chicken, chickpeas, or a mix of vegetables like potatoes, carrots, or spinach directly to the sauce and simmer for another 5-10 minutes to heat through. Garnish with fresh cilantro or parsley and serve over steamed rice.