Butter a casserole dish or cast iron pan.
Brown the bacon strips in a large pan over medium heat. Remove bacon and rough chop.
Saute onion in the same pan you cooked the bacon in, over medium high heat, using the bacon fat to caramelize the onions until just tender.
Beat eggs and heavy cream together in a bowl. Season with a pinch of salt and pepper.
Combine cubed bread, onion, bacon, roasted broccolini and cheeses together. Place in prepared casserole dish or cast iron pan (I like to arrange a few broccolini pieces artistically on top).
Pour egg mixture over bread mixture in prepared pan.
Cover with foil and place in the refrigerator overnight.
When ready to eat, preheat oven to 350 degrees and bake covered for 30 minutes. Remove cover and bake an additional 10-15 minutes until starting to brown. NOTE: If using a cast iron pan, you may need to reduce the cooking time by 5 minutes or so.