In a large pot over medium-high heat, melt the oil and the butter. Add garlic, shallots, and fennel and sauté 10 minutes, or until the vegetables are soft and translucent. Add the rice, thyme, bay leaf, chili, white pepper, lemon juice, and 1 liter of the stock. Turn the heat to medium-low and cook for 20 minutes, or until the rice begins to soften and starts to thicken the soup. Add corn.