I use frozen broccoli and cauliflower making sure the vegetables are completely thawed out before baking. Place the bags in the refrigerator the night before and they will be ready to use when you get started.
If you want to use fresh vegetables, steam them first until they are tender-crisp and then rinse with cold water to stop the cooking process. You don't want mushy veggies in your casserole.
Prepare your 2 quart baking dish by spraying with nonstick spray and preheat the oven to 325 degrees.
In a large skillet, combine soup, sour cream, one cup of the cheese, and 1 1/4 cups of the fried onions. Add the thawed broccoli and cauliflower, season with salt and pepper, and stir until combined. Heat over medium-high heat until the sauce is smooth and blended.
Pour the vegetable mix into your prepared baking dish and bake for 25-30 minutes.
Remove from oven and top with the remaining cheese and fried onions. Pop the dish back into the oven and bake until the cheese is melted and the onions are golden brown, about 5 - 8 minutes.