Preheat the oven to 425 degrees F. Halve the pork tenderloin crosswise; sprinkle with 1 teaspoon thyme and 1/2 teaspoon each salt and pepper. Heat 1 tablespoon olive oil in a large nonstick skillet over medium-high heat. Add the pork and cook, turning, until browned, about 5 minutes. Transfer to a roasting pan; roast until a meat thermometer inserted into the thickest part of the pork registers 140 degrees F, 12 to 15 minutes.
Meanwhile, heat the remaining 1 tablespoon olive oil in a large saucepan over medium heat. Add the fennel, garlic, potatoes, wine and 1 cup water; season with salt and pepper. Stir, then cover and cook, stirring occasionally, until the potatoes are almost tender, 15 minutes.
Uncover and cook until the potatoes are tender, about 10 minutes. Add the broth and the remaining 1/2 teaspoon thyme. Simmer until slightly reduced, 1 minute. Add the cream; increase the heat and gently boil until slightly thickened, about 1 more minute. Season with salt and pepper. Slice the pork and serve with the vegetables and sauce. Top with parsley.