1. Heat coconut oil in a large soup pot over medium heat. Add chopped shallot or onion and sauté until softened, about 3 to 4 minutes. Add garlic and ginger, cooking until fragrant, about 1 to 2 minutes.
2. Stir in red curry paste and cook for an additional minute to release flavors.
3. Slowly pour in broth, scraping any browned bits from the pot bottom. Add coconut milk, tamari, fish sauce, coconut sugar, dried basil, salt, and pepper. Bring to a gentle boil over high heat, then reduce to medium-low and simmer for 10 minutes, stirring occasionally.
4. Increase heat to bring soup back to a rolling boil. Add shrimp, mushrooms (if using), and spinach or chosen vegetables. Cook until shrimp are fully opaque and vegetables are tender, about 4 to 5 minutes.
5. Squeeze juice of half the lime into the soup and stir. Adjust seasoning as needed.
6. Serve soup over cooked rice or cauliflower rice, garnished with fresh cilantro, sliced green onions, and lime wedges.