Step 1

Preheat oven to 350 degrees F.

Step 2

Bring an inch of water to a boil in a large pot fitted with a steamer basket. Add broccoli, cover and steam until just tender, about 5 minutes. Coarsely chop the broccoli.

Step 3

Meanwhile, heat oil in a large saucepan over medium heat. Add onion and cook, stirring, until starting to soften, about 3 minutes. Add garlic and reduce heat to medium-low. Continue stirring until the onion and garlic are starting to brown, about 5 minutes more. Remove from heat.

Step 4

Combine cream cheese, sour cream, 1 cup Cheddar, salt and pepper in a large bowl. Add the onion mixture and stir until well combined. Add the broccoli and stir until coated. Transfer to an 8-inch-square baking dish; sprinkle evenly with the remaining 1/2 cup Cheddar. Bake until the casserole is hot and the cheese has melted, about 25 minutes. Let cool for at least 10 minutes before serving.