Chop ingredients: Start by chopping the fresh broccoli and onion into small, bite-sized pieces. This will help them cook evenly and blend beautifully in the casserole.

Boil broccoli: Add the chopped broccoli and salt to a saucepan, then cover with water. Bring it to a boil and simmer until the broccoli is tender, about 5-7 minutes. Drain well to remove excess water.

Sauté onion: In a skillet, melt the butter over medium heat, then add the chopped onion. Sauté until the onions are golden and tender, about 3-4 minutes, enhancing their sweet flavor.

Beat eggs: In a mixing bowl, crack the eggs and beat them until smooth. This will help bind the casserole together nicely.

Mix in cream: Add the cream of mushroom soup and mayonnaise to the beaten eggs. Stir until the mixture is well combined and silky.

Combine ingredients: Fold in the drained broccoli and sautéed onions into the egg mixture, stirring gently until everything is well blended.

Chill casserole: Pour the mixture into a greased baking dish, cover, and refrigerate overnight. This allows the flavors to meld together beautifully.

Preheat oven: About 45 minutes before you’re ready to serve, remove the casserole from the refrigerator and let it sit at room temperature. Preheat your oven to 350°F.

Add toppings: Sprinkle the crushed saltine crackers and shredded cheddar cheese generously over the casserole. Then, cover the dish with aluminum foil to keep it moist as it bakes.

Bake: Place the dish in the preheated oven and bake for 30-35 minutes, until the casserole is hot and bubbly, and the cheese is melted to perfection.

Cool and serve: After baking, remove from the oven and let it sit for about 10 minutes. This helps the casserole set before serving, making it easier to cut portions.