In a separate bowl, toss together onion, garlic, and 2 teaspoon grapeseed oil. Add to baking sheets. Roast 15 minutes longer, or until pumpkin and onion are tender. Keep an eye on garlic and turn, if necessary, to keep from burning. Transfer to a small Dutch oven or a large saucepan.
Add stock, cinnamon, cardamom, and chile. Bring to a simmer over high flame, reduce heat, and simmer, covered, 20 to 25 minutes, or until pumpkin begins to soften.
Discard cinnamon sticks and cardamom pods. Transfer soup to a blender or food processor and blend until smooth. Mince one sage leaf and add to soup. Season with salt and pepper to taste. Keep warm.
Meanwhile, in a small skillet, heat remaining 1/2 cup grapeseed oil to 350°, or until a sage leaf sizzles when added to oil. Fry remaining sage leaves, 4 at a time, turning once, until crisp, about 1 minute total; do not brown. Drain on paper towels and season lightly with salt and pepper.
Transfer soup to serving bowls and garnish with crispy sage leaves.