I love making Air Fryer Vegan Broccoli Casserole when I want a quick side dish that works for weeknight dinners and holiday meals. Tender broccoli florets get coated in a creamy mushroom sauce with nutritional yeast for rich, almost cheesy flavor, then topped with crispy fried onions that turn golden and crunchy. The best part? No heating up your whole kitchen. Perfect for Thanksgiving, Christmas, Friendsgiving, and potlucks, plus it's budget-friendly and feeds a crowd. Store leftovers in the fridge for up to 4 days or freeze for up to 3 months.
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
In a baking dish that fits your air fryer, combine the blanched broccoli and mushroom sauce. Stir until evenly coated.
Place the dish in the air fryer and cook at 350°F (175°C) for 10 to 15 minutes, or until hot and bubbly.
Sprinkle the crispy fried onions evenly over the top. Air fry for another 3 to 5 minutes, or until the topping is golden and crisp.
1 ½ cups crispy fried onions
Let it rest for a few minutes before serving warm.
Notes
Here are my best tips for making this vegan casserole turn out perfectly every time:
Don't overcook the broccoli: Blanch it for just 4 to 5 minutes so it stays slightly firm, since it'll cook more in the air fryer, and you don't want mushy broccoli.
Brown the mushrooms properly: Let them sit in the pan without stirring too much so they release their moisture and get that golden, caramelized flavor instead of steaming.
Whisk out the lumps: When you add the flour, make sure to whisk constantly as you pour in the liquids so your sauce stays smooth and doesn't get clumpy.
Use the right dish size: Your baking dish should fit comfortably in your air fryer basket with a little space around it for air circulation; otherwise, the casserole won't heat evenly.
Watch the topping closely: Crispy fried onions can go from golden to burnt quickly, so keep an eye on them during the last few minutes of cooking.
Flash freeze for meal prep: If you're freezing portions, spread them on a baking sheet and freeze for 1 hour before transferring to containers so the sauce doesn't stick together in one big clump.