Preheat oven to 425 degrees.

Trim stem end of each Brussels sprout, trim away and blemished leaves, and cut in half. Set aside.

Cut bacon into small pieces. Melt butter in large saucepan and add bacon. Cook over medium heat for 7-8 minutes until crispy.

Add trimmed sprouts and saute for 4 minutes. Add the onion and cook for 2 minutes. Add the garlic and cook 1 more minute.

Add the cream and scrape all the brown bits from the bottom of the pan (the fonde). Bring to a simmer and cook until cream is reduced and coats the sprouts, about 10-12 minutes. Add the mozzarella cheese and stir to melt. Season to taste with salt and pepper. Remove from heat.

Spray a 9" x 13" casserole dish with cooking spray and transfer the mixture. Sprinkle the top with blue cheese crumbles and breadcrumbs. Bake for 20 minutes. Let sit for 5 minutes before serving.