Heat a large saucepan over medium high heat. Add the onion, leeks and butter. Sauté until the vegetables begin to soften. Add the cauliflower, potato and cover with the chicken broth. Add the bay leaf and salt. Bring to a boil. Turn down to a simmer and cook for 15-20 minutes until cauliflower and potatoes are tender. Remove the bay leaf. Puree in batches in blender until smooth. Return to the saucepan. Add the cream, and adjust the seasoning with salt.
Preheat the oven to 400°F. Spread the cauliflower florets out on a sheet pan. Toss with 2 tablespoons of the olive oil and season with salt and pepper. Roast for 15 minutes until starting to brown, stirring occasionally to cook evenly.
While the cauliflower is roasting, heat a large skillet over high heat with the remaining olive oil and pancetta. Cook until crisp. Add the garlic, the roasted cauliflower, the chopped parsley and capers. Toss to evenly coat. Season with the lemon juice. To serve ladle the soup into bowls and garnish with a large spoonful of the roasted cauliflower mixture into the center of each bowl.
Enjoy with a glass of Cakebread Cellars Chardonnay.