Best All-in-One Brunch Casserole
BEST ALL-IN-ONE BRUNCH CASSEROLE12 c. cubed bread (like sourdough, brioche, etc.02 T. olive oil1 c. chopped red onion1 (5-oz.) bag fresh baby spinach1 c. shredded sharp white Cheddar cheese, divided1 c. shredded Swiss cheese, divided1 lb. cubed smoked ham6 eggs4…