Cut solid sections of squashes into large chunks and seed-pod sections into 3/4-inch-thick wedges. Puree onion, garlic, and 1 tablespoon water in a blender until smooth.
Heat oil in a 4-quart pot over medium heat. Add mustard seeds, fennel seeds, and coriander, and cook until fragrant, 1 to 2 minutes. Stir in onion paste and ginger. Cook, stirring often, until caramelized, 6 to 8 minutes.
Add tomato paste, scraping bottom of pot if needed. Stir in remaining 3 cups water, the salt, and crushed red-pepper flakes. Add squash, and cover partially. Bring to a boil. Reduce heat, and simmer gently until squash is tender, 12 to 15 minutes. Serve over brown rice with cilantro and lime wedges.
Delicious recipe! An easy variation that I've tried is to use 1 15 oz can of pumpkin and two chopped sweet potatoes in place of the butternut squash. Enjoy!
This is excellent over broiled or poached cod or tofu. I omitted the rice and served the squash curry directly on top of the cod the first night. This curry become more spicy each day as the flavors of the pepper flakes and ginger expand in the sauce.
I modified the recipe as follows:
-tossed the cut up squash in 1 TBSP cornstarch
-added 1/2 teaspoon turmeric, 1/2 teaspoon allspice, 1/4 teaspoon cloves
-increased coriander and red pepper flakes to 1/2 teaspoon