Cook the elbow macaroni until al dente, 8 or 9 minutes, then drain and set aside.
Preheat oven to 400 degrees and spray 3-quart baking dish with non-stick cooking spray.
Heat milk with 3 sprigs of thyme and 4 cloves of crushed garlic in a small pan, do not boil the milk.
In a large skillet, melt the butter over medium high heat. Once melted, whisk in the flour and cook, stirring constantly for about 1 minute.
Remove the thyme sprigs and garlic cloves from the milk then whisk the milk into the butter and flour mixture.
Continue to cook until the mixture is smooth, whisking constantly. Once smooth, stir in 4-1/2 cups of the white cheddar cheese. Continue to cook and stir until the cheese is melted. Add salt and pepper to taste.
Add in the cooked macaroni and the chopped parsley. Stir to coat the macaroni and incorporate all ingredients then pour into the prepared baking dish and top with the remaining cheddar cheese. Bake for 30 minutes.
Meanwhile, in a saucepan, cook bacon until crispy. Then add the onion, the remaining two cloves of garlic (chopped) and the remaining thyme (leaves only this time). Cook until the onions are soft, about 5 minutes. Season with salt and pepper.
When the macaroni and cheese comes out of the oven, spread the bacon and onion mixture over the top, serve and enjoy.