Savory Mushroom Stroganoff - Jazzy Vegetarian - Vegan and Delicious!

Ingredients

• 1 medium red onion, chopped
• 1/2 tablespoon extra-virgin olive oil (optional)
• 3 to 4 cups vegetable broth, plus more as needed, divided
• 1 teaspoon tamari, divided
• Pinch of cayenne pepper
• 8 ounces Portobello mushrooms, thinly sliced
• 1 teaspoon dried basil
• 8 ounces cremini or white button mushrooms, sliced
• 2 heaping tablespoons whole-wheat flour or oat flour, plus more as needed (use gluten-free oat flour if needed)
• 1⁄2 cup water, plus more as needed
• Salt, to taste
• Freshly ground pepper, to taste