Place the Brussels sprouts in a saucepan with a bit of water and a lid.  Turn them on low-medium heat and steam them until tender.  While that's happening, prepare your sauce.

Cook the bacon in a frying pan over medium-high heat until it's nearly done.  Add the onion and saute until soft, then remove the bacon strips and set them aside.

Add the butter to the pan, then the flour.  Use navy bean flour if you need it to be grain or gluten-free.  Cook for 2 – 3 minutes over medium heat until the roux is smooth.  Add a bit of salt and pepper (you can add more later if desired).

Add the chicken stock and milk, and cook while stirring constantly until smooth.

Add the Brussels sprouts (which should now be done) to an 8×8 casserole dish.  Pour the sauce over them, then sprinkle on the cheddar.  Crumble the bacon over all of it.  Stir to combine.

Top the Brussels sprouts with breadcrumbs (if using) and Romano cheese.  Cover with foil (it won't touch the food) and bake for 30 minutes.  Remove the foil and bake for 10 – 15 minutes longer, until the edges are golden brown.  Serve.