Preheat oven to 350 degrees F.
Cook penne pasta according to package instructions. Drain and set aside.
In a large skillet or saucepan over low heat, add butter once it is almost melted and diced onion. Cook until transparent, about 5 minutes. Season with a pinch of salt and pepper.
Add garlic and cook for another 30 seconds.
Add the flour and stir to distribute flour. Increase heat to medium and cook for a minute or two, stirring continuously.
Slowly stir in warmed cream in a slow drizzle and stir constantly to avoid lumps.
Bring the cream mixture to a very slight simmer and cook until it thickens slightly.
When the sauce is the consistency of gravy, season it with fresh thyme, oregano, and a pinch of salt and pepper.
Please remove it from the heat and stir in parmesan cheese.
Add cooked pasta, ¾ of the pepperoni, 1 cup of shredded mozzarella cheese, and the white pizza sauce to a large bowl and gently toss to combine.
Pour mixture into a greased 9x13'' pan. Sprinkle 1 1/s cup of mozzarella cheese on top (you can use more or less cheese), and top with remaining pepperoni pieces.
Bake for 25-30 minutes or until cheese is golden and bubbling.
For a golden brown top, broil for the last minutes of baking.
