Preheat oven to 400 degrees F.
Place a large, oven-safe skillet over medium heat. Cook chopped bacon for 3-4 minutes or until crispy.
Using a slotted spoon, transfer bacon to a plate lined with a paper towel.
Drain the bacon fat from the pan and add butter. Once melted, add the broccoli florets. Season with salt and pepper, to taste, and stir as it cooks.
Saute for 3-4 minutes. Add in the minced garlic and stir well. Saute 30 seconds, or until fragrant.
Pour in the half and half, stir. Pour in half of the cornstarch slurry and whisk as the sauce simmers and continues to cook down.If the sauce is too thin to your liking, pour in the other half of the cornstarch slurry and stir as it simmers and thickens. Keep in mind, you will be adding 3 cheeses that will help thicken the sauce. So if you're unsure, hold off and add the rest of the cornstarch once the cheeses have melted and it has cooked down a bit.If the sauce gets too thick, simply pour in a splash or two of half and half to thin.
Add the parmesan cheese, cream cheese, and 1/2 cup of pepper jack cheese.
Reduce heat to low and allow to simmer for 3-4 minutes, stirring consistently until the cheeses have melted and the sauce is creamy. For softer broccoli, cover the pan with a lid and allow it to cook 3-4 minutes longer prior to adding bacon and placing into the oven.
Add the bacon back to warm, top with remaining 1/2 cup of pepper jack cheese and place into the oven, uncovered, to bake for 10-15 minutes. Allow the cheese to melt.
If preferred, switch the oven over to broil on low. Broil until the cheese is bubbling and brown. Keep an eye on the dish, as it won't take long to brown the cheese. 1-3 minutes depending on burnt preference.
Remove, garnish with red pepper flakes, black pepper, and parmesan cheese, if desired.