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.

In a small bowl, whisk the yogurt until smooth.

In another small bowl, whisk together the cornstarch and water. Add this mixture plus the egg yolk to the yogurt, mixing until smooth. Gently pour this mixture into the soup pot, whisking continuously. Turn the heat to low and continue to simmer for another 10 minutes. Do not let the soup boil or it will curdle the yogurt. Thin the soup as needed with remaining stock.

Melt the butter in a small frying pan over medium heat. Add the mint and paprika and cook until the mixture foams.

Add the tarragon and cream to the soup and season with salt and pepper to taste. Ladle into bowls and top with a swirl of sizzling butter.