How to cook brussel sprouts au gratin with limited ingredients?

I have a bag of frozen brussel sprouts; sharp cheddar, parm & gouda (and American) cheeses; whole milk, fresh onion & garlic; er; I can make breadcrumbs; but no flour or cream cheese as a lot of recipes call for. CRAVING Brussel Sprouts Au Gratin, though! Oh, and applewood thick cut bacon. Any suggestions/recipes using what I have for a main dish (or side dish)?