Meanwhile, coat the onion slices and the garlic with the 2 teaspoons of grapeseed oil. When the pumpkin is ready, make room on the baking sheet for the onion and garlic, and return the pan to the oven for about 15 minutes longer, or until the pumpkin and onion are tender. Keep an eye on the garlic and turn, if necessary, to keep it from turning dark. Transfer all the vegetables to a large saucepan.
Add the cardamom, cinnamon, chili and stock to the saucepan and bring to a simmer over high heat. Reduce the heat to medium-low and cook, uncovered, for 20-25 minutes, or until the pumpkin cubes begin to dissolve in the liquid.
Remove the cinnamon sticks and discard. Transfer the soup to a blender or food processor and process until smooth, working in batches if necessary
Return the blended soup to the saucepan. Season to taste with salt and pepper. Cover to keep warm.
Add the sage leaves to the 350°F oil and fry for about 1 minute, or until crisp. Using tongs or a slotted spoon, gently remove them from the oil and drain on paper towels. Sprinkle lightly with salt and pepper.
Reheat the soup gently if necessary -- it should be piping hot when served. Ladle into warm soup bowls and garnish with crispy sage leaves. Serve at once.