I love making Vegan Broccoli Casserole because the creamy mushroom sauce tastes so rich without any dairy. The sauce is made with garlic, nutritional yeast, and vegetable broth, and it coats tender broccoli florets perfectly with crispy fried onions on top for crunch. I make this for Thanksgiving, Christmas dinner, holiday potlucks, and weeknight dinners because it's hearty enough to satisfy everyone at the table. It's also freezer-friendly for up to 3 months.
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Instructions
Bring a large pot of salted water to a boil. Add the broccoli florets and cook for 4 to 5 minutes, until just tender. Drain and set aside.
1 pound fresh broccoli florets
Heat olive oil in a large skillet over medium heat. Add the sliced mushrooms and cook for 6 to 7 minutes, until browned. Stir in the minced garlic and cook for another 1 minute.
Sprinkle the flour over the mushrooms and stir well to coat. Gradually whisk in the vegetable broth and plant-based milk until smooth.
2 tablespoons all-purpose flour, 1 cup vegetable broth, 1 cup unsweetened plant-based milk
Add the nutritional yeast, soy sauce, onion powder, salt, and black pepper. Simmer for 5 to 7 minutes, stirring occasionally, until the sauce thickens.
2 tablespoons nutritional yeast, 1 tablespoon soy sauce, 1 teaspoon onion powder, Salt and black pepper
Spread the blanched broccoli evenly in a casserole dish. Pour the mushroom sauce over the top and stir gently to combine.
Bake in a preheated oven at 375°F (190°C) for 20 minutes, or until hot and bubbly.
Remove from the oven and top with crispy fried onions. Serve warm.
1 ½ cups crispy fried onions
Notes
Here are my top tips for ensuring this casserole turns out perfectly every time.
Don't skip blanching: Blanching the broccoli first ensures it's tender throughout and keeps it bright green, rather than turning dull olive in color, which often happens when raw broccoli is overcooked.
Brown the mushrooms properly: Let them sit undisturbed for a few minutes at a time, allowing them to caramelize instead of steaming. You want deep golden edges for maximum flavor.
Whisk constantly when adding liquid: Pour the broth and milk gradually while whisking to avoid lumps in your sauce. If you dump it all in at once, the flour can clump up.
Adjust the thickness: If your sauce seems too thick, add a splash more plant-based milk. If it's too thin, let it simmer an extra few minutes before assembling the casserole.
Add onions at the end: Wait until after baking to add the crispy onions. If you put them on before baking, they'll get soggy instead of staying crunchy.
Storage instructions: If you're freezing individual portions, first freeze them uncovered on a baking sheet for 1 hour, then transfer them to containers to prevent them from sticking together and to easily grab just what you need.