Creamy Parmesan Brussels Sprouts Casserole

The kitchen smelled like butter and thyme before I even realized what was happening, and by then the casserole was already half gone from the serving dish. My sister in law, who swore she hated Brussels sprouts, went back for thirds at Thanksgiving and refused to believe me when I told her what was in it. That golden, bubbling Parmesan crust has a way of making honest people into liars.

One December I made this three weekends in a row because my neighbor kept appearing at my door around dinnertime with increasingly thin excuses about borrowing things. I finally just started making a double batch and leaving a plate on the porch.

Ingredients

• 1 1/2 lbs Brussels sprouts, trimmed and halved: Pick ones that are tight, bright green, and small, since they tend to be sweeter and cook more evenly.
• 1 medium onion, finely chopped: A yellow onion adds sweetness that balances the earthy sprouts perfectly.
• 3 cloves garlic, minced: Fresh garlic makes a difference here, so skip the jarred stuff if you can.
• 1 1/2 cups heavy cream: This is what makes the sauce luxuriously velvety and coats every single sprout.
• 3/4 cup grated Parmesan cheese (for sauce): Grate it yourself from a block for the best melting and flavor.
• 1 cup shredded mozzarella cheese: Mozzarella adds stretch and mellowness that keeps the Parmesan from taking over completely.
• 2 tbsp unsalted butter: This is your flavor foundation for the onion and garlic, so use good quality butter.
• 1 tsp salt: Kosher salt gives you more control over seasoning than table salt.
• 1/2 tsp black pepper: Freshly cracked is always better, and you will notice the difference in a cream sauce.
• 1/2 tsp dried thyme: Thyme and Brussels sprouts are old friends, and that herbal note ties everything together.
• 1/4 tsp ground nutmeg: Just a whisper of nutmeg in cream sauce is an old trick that makes people wonder what your secret is.
• 1/2 cup panko breadcrumbs: Panko stays crispier than regular breadcrumbs, which is exactly what you want on top.
• 1/4 cup grated Parmesan cheese (for topping): This creates that irresistible golden cheese crust.
• 1 tbsp olive oil: Mixing this with the panko ensures an even, crunchy topping.

Instructions

Get your oven ready:

Preheat to 400 degrees F and lightly grease a 9 by 13 inch baking dish so nothing sticks when you serve it.

Blanch the sprouts:

Drop the halved Brussels sprouts into a large pot of salted boiling water for 3 to 4 minutes until they are just tender and still bright green, then drain them well.

Build the flavor base:

Melt the butter in a large skillet over medium heat, then sauté the chopped onion for 3 to 4 minutes until it turns translucent and sweet before adding the garlic for one more minute.

Make it creamy:

Pour in the heavy cream and bring it to a gentle simmer, then stir in the Parmesan, mozzarella, salt, pepper, thyme, and nutmeg until the cheese melts into a thick, glossy sauce.

Combine and transfer:

Toss the blanched sprouts in that beautiful sauce until every piece is coated, then spread the whole thing into your prepared baking dish.

Build the topping:

Mix panko, the remaining Parmesan, and olive oil in a small bowl until it looks like wet sand, then sprinkle it evenly across the top of the casserole.

Bake to golden perfection:

Slide it into the oven for 20 to 25 minutes until the edges are bubbling and the top is deeply golden, then let it rest for a few minutes before serving so the sauce settles.

Save

There is something about carrying a bubbling, golden topped casserole from the kitchen to the table that makes everyone in the room go quiet in anticipation. That dish became my signature contribution to every family gathering, and I stopped being asked to bring rolls a long time ago.

Variations Worth Trying

Stirring in a handful of cooked, chopped bacon or crispy pancetta transforms this from a side dish into something that could steal the entire meal. I once used Gruyere instead of mozzarella on a whim and ended up with a sauce so complex and nutty that my father in law asked if I had ordered it from a restaurant.

Serving Suggestions

This casserole sits proudly next to roasted turkey, a glazed ham, or even a simple roast chicken without competing for attention. For a vegetarian dinner, pair it with a bright, lemony salad and some crusty bread to soak up every bit of that cream sauce.

Make Ahead and Storage

You can assemble the entire casserole up to a day ahead and keep it covered in the fridge, then just add the topping and bake when you are ready. Leftovers keep well for three days and reheat beautifully in the oven at 350 degrees F.

• Let the casserole come to room temperature for about 30 minutes before baking if it has been in the fridge.
• Cover with foil for the first 15 minutes of reheating to prevent the top from burning.
• Always add the panko topping fresh right before baking for maximum crunch.

Save

Every time I make this casserole, I think about how the simplest dishes, when made with care and a little cream, become the ones people remember most. Keep this one in your back pocket for any night that calls for something warm and golden.

Recipe Questions & Answers

→ How should I trim and prepare Brussels sprouts?

Trim the stem end, remove any loose outer leaves, and halve larger sprouts so they cook evenly. Smaller ones can be left whole. Blanching for 3–4 minutes softens them slightly and shortens bake time.

→ What’s the purpose of blanching the sprouts?

Blanching briefly softens the interior while preserving color and reduces overall oven time. It also helps the sprouts absorb the creamy sauce so they remain tender rather than drying out in the bake.

→ How can I get a crunchier topping?

Toss the panko with olive oil or melted butter before sprinkling and toast it briefly in a skillet for extra color. For an extra crisp finish, broil 1–2 minutes at the end, watching closely to avoid burning.

→ What are good cheese substitutions?

Swap mozzarella with Gruyère or Swiss for nuttier notes, and try Pecorino in place of some Parmesan for sharper flavor. Reduce added salt if using saltier cheeses.

→ Can this be made ahead?

Assemble the dish up to 24 hours ahead, cover and refrigerate, then bake from chilled—add a few extra minutes to the bake. For longer storage, freeze before baking for up to 2 months and bake from frozen with additional time.

→ How should leftovers be stored and reheated?

Cover and refrigerate leftovers for 3–4 days. Reheat in a 350°F (175°C) oven until warmed through to preserve texture; microwaving is quicker but may soften the topping.