Can I make this casserole ahead of time?
Yes. Assemble the casserole up to 24 hours in advance, cover, and refrigerate. Add 5–10 extra minutes to baking time if baking from cold.
Can I use fresh green beans instead of frozen?
Yes. Use 2 lbs fresh green beans, trimmed and blanched for 4–5 minutes until tender-crisp, then drained well.
What can I substitute for sharp cheddar?
Gruyère, aged gouda, or fontina work well. Avoid mild cheddar, which won't deliver enough flavor.
How do I cook the bacon ahead?
Cook bacon the morning of and store in the fridge; crumble just before mixing into the casserole to keep it crisp.
Can I use canned cream of mushroom soup instead?
Yes, but reduce it slightly (use ¾ can + ¼ cup sour cream) to avoid excess liquid, since canned soup is thinner than homemade.