Sweet Potato Soup

Name: Sweet Potato Soup
Ingredients: 2 pounds sweet potatoes (about 2 large); 2 tablespoons plus 1 teaspoon olive oil, divided; 2 teaspoons kosher salt, divided; 1 teaspoon freshly ground black pepper, divided; 1 medium yellow onion; 6 large cloves garlic; 1 (4-inch) piece ginger; 1 tablespoon unsalted butter; Pinch red pepper flakes, plus more as needed (optional); 1/2 teaspoon garam masala; 1/2 cinnamon stick; 1 (32-ounce) carton low-sodium vegetable or chicken broth (about 4 cups); 1/4 cup heavy cream, plus more for serving; Toasted bread, for serving (optional)