Preheat the oven to 400°F.
In a skillet over medium heat, cook the bacon, until golden brown, about 8 minutes. Drain bacon on absorbent paper towels and reserve.
In a saucepan over medium heat, melt the butter and add the cornstarch. Stir and cook for 1 minute, to make a roux.
Slowly add the milk and cook stirring constantly for about 5 minutes until the béchamel begins to thicken.
Add salt and nutmeg and stir. Remove from the fire.
Add the cheese and stir until melted.
In a bowl, mix the pasta with the bacon and add the cheese sauce. Stir well.
Pour into a 10 x 14 inch pan and bake for 15-20 minutes until evenly browned.
Remove from the oven and let cool for 10 to 15 minutes before serving.