Place the first 6 ingredients into a large pressure cooker, seal, and bring to high pressure. Reduce heat to maintain high pressure for 8 minutes. Remove from heat and allow pressure to come down naturally while you prepare the remaining ingredients. (For stove-top cooking, simmer until split peas are tender, about 30 to 45 minutes.)
When the pressure is down, use a hand blender to puree the soup. Or, blend in batches in a regular blender—be careful because this is hot and splatters easily. Add the next 6 ingredients (*and the dried basil, if you're using it) and cook for about 30-45 minutes, until greens are completely tender. Add additional water if necessary to prevent soup from becoming too dry.
Add the remaining ingredients and use your blender again to puree the greens and mushrooms until fairly smooth. Check seasoning and add salt as needed, and thin with a little water if you find it too thick. Serve with additional lemon or try it with a spoonful of plain soy yogurt stirred in.
Makes 4-6 servings. Based on 4 servings, without salt, this provides: 290 Calories (kcal); 4 g Total Fat; (11% calories from fat); 18 g Protein; 52 g Carbohydrate; 0 mg Cholesterol; 89 mg Sodium; 20 g Fiber.
Want to see how healthy this soup is? Based on a 2000 calorie-per-day diet, it provides 41% of your calcium, 23% of iron, 167% of vitamin C, 612% of vitamin A (i.u.), 212% vitamin B6, 50% vitamin B12, and 143% of folicin. The only thing it's low in is sodium!