Heat a Dutch oven over medium heat. Add the pancetta and saute for about 8 minutes, until crisp and some of the fat has rendered. Remove with a slotted spoon and set aside. Add the fennel to the pan and sweat for about 5 minutes, stirring often without browning. Add the leeks and sweat for 5 to 8 minutes, until both vegetables are tender. Add the thyme and garlic and saute for about 1 minute, until fragrant. Add potatoes, broth and reserved clam juice into vegetables. If there’s not enough liquid to cover the potatoes, add a little water. Bring to a simmer and cook uncovered, stirring occasionally, for 12 to 15 minutes, until potatoes are tender. Add clams and pancetta; simmer for 2 minutes. Stir in milk and bring to a simmer. Season with salt, pepper and Tabasco. Serves 12.