A creamy, cheesy cauliflower bake that’s quick to prepare, full of flavor, and perfect as a satisfying side or vegetarian main. Roasted florets meet a rich cheese sauce, then bake to golden perfection with a crispy topping. Ideal for everyday dinners or meal prep.
2small cauliflower headstrimmed and cut into bite-sized florets
1cupfrozen pearl onionsthawed
3 ½tablespoonsunsalted butter
3tablespoonsall-purpose flour
2cupsmilk
2teaspoonsDijon mustard
4ouncesGruyere cheeseshredded
4ouncescheddar cheeseshredded
3green onionsthinly sliced
1cupcrispy fried onions
Saltto taste
Pepperto taste
Instructions
Preheat and Prepare Oven: Begin by preheating your oven to 375°F (190°C) to ensure it reaches the ideal roasting temperature. While the oven warms, make sure your cauliflower heads are trimmed, the florets are bite-sized, and your pearl onions are thawed. Preheating is crucial for achieving a slightly caramelized exterior on your vegetables, which enhances flavor and texture in the final bake.
Toss Vegetables with Oil and Seasoning: In a large mixing bowl, combine the cauliflower florets and thawed pearl onions. Drizzle 2 ½ tablespoons of extra virgin olive oil over the vegetables. Sprinkle with a pinch of salt and freshly ground black pepper. Using clean hands or a large spoon, toss the mixture thoroughly until every floret and onion is evenly coated with oil and seasoning. This step ensures even roasting and maximizes the flavor of the vegetables.
Spread Vegetables on Baking Sheet: Line a baking sheet with parchment paper or lightly grease it to prevent sticking. Arrange the coated cauliflower and onions in a single, even layer. Avoid overcrowding the pan; each piece should have space to roast rather than steam. Proper spacing allows the vegetables to caramelize beautifully and maintain a slight bite, which will provide texture in the final creamy dish.
Roast Vegetables Until Tender: Place the baking sheet in the preheated oven and roast for 25–30 minutes. Halfway through, gently shake or stir the vegetables to promote even cooking and golden edges. The cauliflower should be lightly browned, slightly crisp at the tips, but still tender in the center. Remove from the oven and allow them to cool slightly while you prepare the cheese sauce.
Make a Roux Base for Sauce: In a medium saucepan, melt 3 ½ tablespoons of unsalted butter over medium-low heat. Once melted, sprinkle 3 tablespoons of all-purpose flour into the butter. Whisk continuously for about one minute until the flour is fully incorporated, creating a smooth paste, or roux. Cooking the roux briefly removes the raw flour taste and sets the foundation for a creamy sauce.
Incorporate Milk and Simmer: Slowly pour 2 cups of milk into the roux, whisking constantly to prevent lumps. Continue whisking until the mixture is perfectly smooth. Increase the heat slightly and allow the sauce to simmer gently, stirring occasionally, until it thickens to a creamy consistency that lightly coats the back of a spoon. A thick sauce will cling to the cauliflower beautifully in the final bake.
Flavor the Sauce: Stir in 2 teaspoons of Dijon mustard, then season with salt and black pepper to taste. The mustard adds a subtle tang and depth, enhancing the richness of the cheeses. Mix thoroughly until the sauce is smooth, flavorful, and ready for the cheese.
Melt Gruyere Cheese Into Sauce: Remove the saucepan from heat temporarily and begin incorporating 4 ounces of shredded Gruyere cheese in small handfuls. Stir each addition until fully melted before adding more. This gradual method ensures a silky, lump-free cheese sauce with a rich, nutty flavor.
Add Cheddar and Green Onions: Once the Gruyere has fully melted, stir in half (2 ounces) of the shredded cheddar cheese and half of the sliced green onions. Mix gently until the sauce is smooth and evenly blended. The cheddar adds a sharp, creamy flavor, while the green onions provide freshness and subtle crunch.
Combine Roasted Vegetables and Cheese Sauce: Transfer the roasted cauliflower and pearl onions into the prepared cheese sauce. Using a spatula or large spoon, fold the vegetables gently until they are fully coated. Be careful not to mash the florets; the goal is to maintain texture while ensuring every piece is enveloped in creamy, cheesy goodness.
Transfer to Baking Dish: Lightly grease a 9x13-inch baking dish. Pour the vegetable and cheese mixture into the dish, spreading it evenly. A level surface ensures even baking and a uniform golden top.
Top with Cheese and Crispy Onions: Sprinkle the remaining 2 ounces of shredded cheddar over the top of the casserole. Evenly distribute 1 cup of crispy fried onions for a crunchy, flavorful topping. The topping will brown beautifully during baking, adding both texture and visual appeal.
Bake Until Golden and Bubbling: Place the casserole in the oven and bake for 15 minutes. Keep an eye on the top; it should turn golden brown and begin bubbling at the edges. This step melds the flavors together and creates a comforting, visually appealing dish.
Garnish and Serve: Remove the baked cauliflower from the oven and sprinkle the remaining sliced green onions on top. Add an extra grind of black pepper if desired. Allow the casserole to cool slightly for 5 minutes before serving. This rest time lets the sauce thicken slightly and makes serving easier while keeping the dish creamy and luscious.
Notes
For best results, choose fresh cauliflower heads that are firm, white, and free from brown spots. Smaller florets roast more evenly and absorb the cheese sauce better.
Thaw frozen pearl onions completely before roasting to prevent excess water from diluting the sauce.
Use a mix of Gruyere and cheddar for depth of flavor; Gruyere adds nuttiness, while cheddar provides sharpness.
Lightly greasing the baking dish prevents sticking and makes cleanup easier.
If desired, add a pinch of smoked paprika or nutmeg to the cheese sauce for extra warmth and complexity.
Crispy fried onions are key for texture; if unavailable, substitute with toasted breadcrumbs for a crunchy topping.