Begin by steaming or blanching the broccoli florets in boiling water for 3–5 minutes until vibrant green and tender. Drain thoroughly to remove excess moisture.

In a large skillet, heat olive oil or butter over medium heat. Add sliced onions, sprinkle with salt and sugar, and sauté for 15–20 minutes until golden brown and caramelized.

In a mixing bowl, combine cooked broccoli, caramelized onions, and shredded cheddar cheese. Pour in milk or cream, followed by salt and pepper. Stir until well mixed.

Grease a baking dish, then pour the broccoli and cheese mixture into it. Spread evenly using a spatula.

Sprinkle fried onions evenly over the top of the casserole. Optionally, drizzle melted butter for added richness.

Preheat oven to 350°F (175°C). Bake the casserole for 30–40 minutes until the top is golden brown and cheesy aroma fills the kitchen.