In a large pot, heat olive oil. Add sliced onion; sauté 7 minutes.
Add butternut squash pieces and cauliflower florets; cook 12 minutes, until softened. Add curry powder, salt, ground ginger, sugar and cayenne and cook, stirring, 1 minute.
Place 1/4 reduced-sodium vegetable broth in a small measuring cup and stir in cornstarch. Set aside.
Add another 1 1/2 cups broth, chickpeas and diced tomatoes to pot and bring to a boil. Cover and reduce heat to medium-low. Simmer 12 minutes, until veggies are tender.
Stir in cornstarch mixture and baby spinach. Stir until spinach is wilted and mixture has thickened.