1Preheat oven to 350 degrees.Grease a 9x13-inch baking dish,and sprinkle with 1 tablespoon grated parmesan cheese around the inside of the dish.Add grilled cheese sandwich bits,mix well.
2Fill a large pot with lightly salted water and bring to a rolling boil.Once the water is boiling,stir in the penne,and return to a boil.Cook the penne uncovered,
stirring occasionally,until pasta has cooked through,but is still firm to the bite,about 11 minutes.Drain well in a colander set in the sink.
3Place the bacon pieces into a large,deep skillet,and cook medium-high heat,stirring occasionally,until evenly browned,about 10 minutes.Drain the bacon slices
on a paper towel-lined plate.Retain 1/4 cup of bacon drippings.Set the bacon pieces aside.
4Melt butter and bacon drippings together in a large saucepan over medium heat,about cook and stir in carrot,about 5 minutes.Whisk in the flour,stirring frequently,until the mixture forms a smooth paste.
Whisk in the milk,a little at a time,and bring the mixture to a simmer,whisking constantly until thickened.Stir in the basil and seasoned pepper,and then whisk in 1/4 cup crumbled blue cheese and 3 cup cheddar cheese,stirring constantly until the cheeses has melted and the sauce is smooth and thick.
5Stir the cooked penne pasta into the cheese sauce,then lightly mix in the cooked bacon.Spread the mixture into
the prepared dish and sprinkle with 1/4 cup cheddar cheese over the top.Cover the dish with foil.Bake in the preheated oven until the pasta is hot and bubbling,about 25 minutes.