Bring a large pot of water to a boil over high heat. Line a plate with paper towels.
In a large skillet, heat 1 tablespoon oil over medium-high heat. Cook the pancetta until brown and crispy, stirring frequently, about 5 minutes, taking care not to burn. Using a slotted spoon, transfer the pancetta to the paper towel-lined plate to drain. Discard the fat in the skillet. Let the skillet cool slightly, then wipe it out with a paper towel.
Add 1 tablespoon salt and the pasta to the pot of boiling water. Cook until al dente, about 1 minute less than the directions on the package. Reserve 1/2 cup pasta water and drain the pasta in a colander.
Heat the remaining 2 tablespoons oil in the skillet over medium heat. Add the garlic and stir for 30 seconds. Add the spinach and mix well. Add the cream and stir until well heated, 2 to 3 minutes.
Season with nutmeg, 1/2 teaspoon salt and 1/8 teaspoon pepper. Reduce the heat to low and add the cooked pasta. Stir in 3 tablespoons of the reserved pasta water. Add the butter and 1/4 cup Parmesan cheese, stirring to make a creamy sauce. If the mixture seems dry, add additional pasta water.
Transfer the pasta to a serving bowl. Scatter the pancetta over the top and sprinkle with the remaining Parmesan cheese and freshly ground pepper. Serve hot.