Using a non-stick skillet on medium-high heat, sauté onion for 2-3 minutes, until it begins to soften and brown on a few edges. Add squash and garlic and cook, stirring, until squash is softening. Add 1 cup corn and remove from heat.
Preheat oven to 350F. Line a 1 1/2 to 2-quart baking dish with parchment paper or oil it lightly.
Blend 1/2 cup corn, vegetable broth, cashews/tofu, cornstarch, lemon juice, and seasonings (nutritional yeast, oregano, thyme, salt, black pepper) in a blender until smooth. TIP: If you don't think your blender will blend raw cashews, soften them first by soaking in water for 2 hours and then draining before use.)
Place half the squash mixture in a single layer in the casserole dish; spoon half of the sauce over it. Repeat with remaining squash and sauce. If you’re using the topping, mix the panko with basil and oregano, and sprinkle it over the top of the casserole. Bake at 350 for 25-30 minutes. If the topping isn't completely browned, heat it under the broiler for a minute or two but watch it carefully to make sure it doesn't burn. Serve hot.
For gluten-free, use gluten-free bread crumbs or omit the topping.Nutritional Info below includes cashews and salt. When made with firm tofu instead of cashews, these are the correct values: