In a small skillet over medium-high heat, add the pancetta and 2 tablespoons of the olive oil and cook until the pancetta is crispy. Transfer the pancetta to a heat-resistant bowl. Be sure to save the renderings for garnish.
In a large Dutch oven over medium-high heat, add the remaining tablespoon of olive oil. Add the carrots, celery and shallots and cook for 6 to 8 minutes. Add the thyme leaves and garlic and cook until fragrant, about 1 minute. Slowly sprinkle in the flour while stirring; it will immediately thicken and get pasty. Slowly add the white wine, stirring to avoid clumping, and reduce for 1 minute. Add the stock and clam juice, bring to a simmer and cook, stirring, until the carrots soften, 5 to 10 minutes. Add the potatoes, bring to a boil, reduce the heat and simmer until the potatoes are tender, about 45 minutes.
Add the clams and cream and stir to incorporate. Cook for about 5 minutes at a low simmer. Season to taste with salt and pepper. Grate in the nutmeg and add three-quarters of the pancetta. Garnish each serving with additional pancetta, a drizzle of the reserved renderings and some chopped parsley.