In a large saute pan over medium high heat cook the pancetta until it begins to brown and crisp. Add the onion and garlic and cook until translucent, about  2 to 3 minutes. Add the spinach to the pan and continue to cook until the spinach is completely wilted and some of the liquid has cooked off, another 2 to 3 minutes. Turn off the heat and add the walnuts and 1 1/2 packages of Boursin cheese. Season with 1 teaspoon salt and 1/2 teaspoon black pepper. Stir the mixture until the Boursin is completely melted. Add the bread and stir to mix well. Let the mixture stand until it reaches room temperature.

Preheat the oven to 350°F.

On a large cutting board, place the turkey breast, skin side down, on top of a piece of plastic wrap. Cut the tenders from the breast and save them for another use. Cover the turkey breast with additional plastic wrap, and, using the smooth side of a meat mallet, pound it to an even thickness of a little less than 1⁄2 inch (you’re going to want to channel every bit of your latent aggression because you need to really strong-arm that mallet to get the breast to that thickness), forming a roughly rectangular piece of meat.

Remove the plastic wrap from on top of the turkey, and season both sides of the turkey evenly with the salt and pepper. Spread the stuffing down the length of the turkey in the center, then roll one side up and over the stuffing and continue rolling the entire thing into a long cylinder. Tie the roulade every couple of inches using kitchen twine.

Set the roulade on a wire rack set in a roasting pan, and bake until an instant-read thermometer inserted in the center reads 155 °F, 50 to 60 minutes. Remove the pan from the oven and let rest for at least 15 minutes before cutting across into 1-inch-thick slices.

Once the turkey is cooked make the sauce by combining the white wine, white wine vinegar, shallots and thyme in a small sauce pan. Bring to a simmer and reduce the liquid until you have about 3 tablespoons. Stir in the remaining Boursin cheese and the heavy cream. Remove from the heat. If the sauce is too thick add a little more cream or any pan drippings leftover from the turkey.

Serve the turkey with the wine sauce.