This Vegetarian Broccoli Cheddar Casserole is surprisingly easy to make, even for beginner cooks. Follow these detailed instructions to create a perfectly cheesy and comforting dish every time:

Step 1: Prepare the Broccoli

• If using fresh broccoli: Wash the broccoli florets thoroughly and cut them into bite-sized pieces. You can steam, boil, or microwave the broccoli until it is tender-crisp. Steaming is often preferred as it retains more nutrients and flavor. Steam for about 5-7 minutes, or until just tender. You want it slightly undercooked as it will continue to cook in the oven.
• If using frozen broccoli: No need to thaw it! You can add frozen broccoli directly to the casserole, but pre-cooking it slightly will prevent it from making the casserole watery. You can steam or microwave the frozen broccoli for a few minutes until partially thawed and slightly tender-crisp. Drain any excess water.

Step 2: Sauté Aromatics

• In a large, oven-safe skillet (cast iron works wonderfully) or a large saucepan, melt the butter over medium heat.
• Add the diced onion and sauté until softened and translucent, about 5-7 minutes. Stir occasionally to prevent burning.
• Add the minced garlic and sauté for another minute until fragrant. Be careful not to burn the garlic, as it can become bitter.

Step 3: Make the Cheddar Cheese Sauce

• Sprinkle the all-purpose flour over the sautéed onions and garlic in the skillet. Cook, stirring constantly, for about 1-2 minutes. This creates a roux, which is essential for a smooth, creamy sauce.
• Slowly whisk in the milk, a little at a time, ensuring each addition is fully incorporated before adding more. This prevents lumps from forming.
• Continue whisking until the sauce is smooth and starts to thicken slightly.
• Gradually whisk in the vegetable broth, again ensuring it’s fully incorporated.
• Bring the sauce to a simmer, stirring constantly, and cook until it thickens to your desired consistency. This usually takes about 5-7 minutes. The sauce should be thick enough to coat the back of a spoon.
• Remove the skillet from the heat.
• Stir in about 3 cups of the shredded cheddar cheese, a handful at a time, until melted and smooth. Reserve the remaining 1 cup of cheese for the topping.
• Season the cheese sauce generously with salt and black pepper to taste. Don’t be shy with the seasoning, as it will enhance the overall flavor.
• If using, stir in a pinch of nutmeg, paprika, and mustard powder for extra flavor depth. Taste and adjust seasonings as needed.

Step 4: Assemble the Casserole

• Add the cooked broccoli florets to the cheese sauce in the skillet. Gently stir to combine and ensure the broccoli is evenly coated in the sauce.
• If you are using an oven-safe skillet, you can proceed directly to the next step. If not, transfer the broccoli and cheese sauce mixture to a greased 9×13 inch baking dish.

Step 5: Prepare the Crispy Topping

• In a small bowl, combine the bread crumbs, remaining 1 cup of shredded cheddar cheese, and olive oil (or melted butter). Toss to combine, ensuring the bread crumbs are evenly coated.

Step 6: Bake the Casserole

• Sprinkle the bread crumb topping evenly over the broccoli and cheese mixture in the skillet or baking dish.
• Bake in a preheated oven at 375°F (190°C) for 20-25 minutes, or until the topping is golden brown and bubbly, and the casserole is heated through.
• If the topping is browning too quickly, you can loosely tent the casserole with aluminum foil for the last 10 minutes of baking.

Step 7: Rest and Serve

• Remove the casserole from the oven and let it rest for 5-10 minutes before serving. This allows the sauce to set slightly and makes it easier to serve.
• Serve hot and enjoy the cheesy, comforting goodness of your Vegetarian Broccoli Cheddar Casserole!