Baked Penne a la Carbonara- Diane Phillips

I've been enjoying Diane Phillips books lately. This is 1 I've made twice in 2 weeks (per family request!)

Serves 10 as a side dish or 6 as a main dish
(Or 4 if you have teen boys!)

1/2 cup (1 stick) unsalted butter
1/2 cup chopped shallots
1 teaspoon chopped fresh thyme
1/4 cup flour
1-1/2 cups heavy cream
1/2 cup chicken broth (Keep some extra handy in case you need to thin out the sauce)
1-1/2 cups freshly grated Parmesan (okay do 2 cups- you're welcome)
1/2 to 1 teaspoon freshly ground black pepper, to taste
Salt (optional) to taste....since when was salt an option?
1 pound penne pasta, cooked according to package directions until al dente and drained
12 strips bacon, cut into 1/2-inch pieces, coked until crisp, and drained on paper towels (app. 3/4 pound)
1/2 pound fresh mozzarella cheese, cut into 1/2-inch cubes

Step 1
In a 3-quart saucepan over medium heat, melt the butter, add the shallots and thyme, and cook, stirring, until softened, about 3 minutes. Whisk in the flour and cook, stirring constantly, until the flour is cooked, but hasn't turned color, 3 to 4 minutes. Stir in the cream and broth and bring to a boil, whisking constantly. Stir in 1 cup of the Parmesan and season with pepper and with salt if desired.

Step 2
Coat a 13x9-inch baking pan with non-stick cooking spray and sprinkle 1/4 cup of the remaining Parmesan over the bottom. In a large bowl, toss the hot penne with the olive oil. (This parmesan makes a nice crust on the bottom.)

Step 3
Stir the sauce into the penne, then stir in the bacon and mozzarella. Transfer to the prepared pan and sprinkle with the remaining 1/4 - 1/2 cup of Parmesan.

Diva Do-Ahead: At this point, you can cover and refrigerate overnight OR freeze freeze for up to 6 weeks. Bring to room temperature before continuing.(Thaw 1 day in fridge)

Step 4
Preheat the oven to 350°F. Bake the penne until golden brown, about 30 minutes. Let rest for about 5 minutes before serving.

Now I was lazy and copied the recipe from here. It looks like a nice blog. Her recipe had olive oil, mine doesn't (I went to Diane's class,where this recipe came from her book) I think the olive oil is why the sauce separated.
Diane's book is called "Perfect Party Food" by Diane Phillips.