Ingredients

- 8 +

• 2 pounds pearl or baby onions, peeled and trimmed carefully
• 1 cup (2 sticks) unsalted butter for browning, divided into quarters
• 24 fresh sage leaves, divided - half roughly chopped and half kept whole for garnish
• 3 cups heavy cream at room temperature
• 2 cups freshly grated Parmesan cheese, divided for layering
• 1 cup seasoned breadcrumbs for a crispy golden topping
• 4 large cloves of garlic, finely minced
• 2 teaspoons fresh thyme leaves, stripped from stems
• 1 teaspoon freshly ground black pepper
• 2 teaspoons kosher salt, divided for layering
• 1/2 teaspoon freshly grated nutmeg
• 3 tablespoons all-purpose flour for thickening

Instructions

1

Begin by blanching the pearl onions in boiling salted water for 3 minutes, then shock in an ice bath and peel carefully

✓ Done

2

In a large skillet over medium heat, brown the butter until it becomes golden and smells nutty, about 5-7 minutes, watching carefully to prevent burning

✓ Done

3

Add the chopped sage leaves to the brown butter and cook for 30 seconds until fragrant and slightly crispy

✓ Done

4

Transfer the onions to a large mixing bowl and toss with half the brown butter-sage mixture, 1 teaspoon salt, and pepper until evenly coated

✓ Done

5

Preheat your oven to 375F and butter a 9x13 inch casserole dish generously

✓ Done

6

Whisk the flour into the remaining brown butter, then gradually add the cream, stirring constantly to create a smooth sauce

✓ Done

7

Add half the Parmesan cheese, garlic, thyme, remaining salt, and nutmeg to the sauce, stirring until the cheese melts completely

✓ Done

8

Layer the seasoned onions in the prepared casserole dish, then pour the cream sauce evenly over the top

✓ Done

9

Sprinkle with remaining Parmesan cheese and seasoned breadcrumbs for a golden crust

✓ Done

10

Bake for 45-50 minutes until bubbly and golden brown on top, with the onions tender when pierced

✓ Done

11

Let rest for 15 minutes before serving to allow the sauce to thicken properly

✓ Done

Kitchen Tools

• 9x13 inch ceramic or glass baking dish
• Large skillet for browning butter
• Heavy-bottomed saucepan for cream sauce
• Sharp paring knife for trimming onions
• Wire whisk for sauce preparation
• Large mixing bowls for combining ingredients

Chef's Tips

To easily peel pearl onions, score an X on the root end before blanching for quick removal of skins

Watch the butter carefully while browning - it can go from perfect to burned very quickly

Use room temperature ingredients for the smoothest sauce consistency

For extra richness, add a splash of white wine to the cream sauce

🔧 Troubleshooting Tips

️

If sauce is too thin, continue baking uncovered for 5-10 minutes longer

️

If top browns too quickly, cover with foil for remaining cooking time

️

If onions are still firm, cover and continue cooking until tender

️

If sauce separates, whisk in a small amount of hot cream to re-emulsify

🔄 Recipe Variations

Add mushrooms for an earthier flavor profile

Include pancetta or bacon for a smoky meat version

Mix in roasted garlic instead of fresh for mellower flavor

Use different fresh herbs like rosemary or tarragon for variety

🥗 Healthy Alternatives

Substitute half the heavy cream with whole milk or half-and-half to reduce calories

Use whole wheat breadcrumbs instead of regular for added fiber

Replace half the Parmesan with nutritional yeast for a lower-fat option

Consider using olive oil instead of some of the butter for healthier fats

🍽️ Serving Suggestions

Serve alongside herb-roasted chicken or grilled steak for a complete meal

Pair with a light arugula salad dressed with lemon vinaigrette to cut through the richness

Complement with roasted root vegetables for a fall-inspired dinner

Offer crusty whole grain bread on the side to soak up the delicious sauce

Nutrition Facts

425

Calories

12g

Protein

18g

Carbs

35g

Fat

🥗 Suitable Diets

Vegetarian-friendly main dish or side dish

Can be adapted for gluten-free diets by using gluten-free breadcrumbs

Not suitable for vegan or dairy-free diets without major modifications

Low-carb option when served without breadcrumb topping

🎨 Presentation Ideas

Top with crispy fried sage leaves

Sprinkle with fresh thyme leaves

Add a drizzle of additional brown butter

Finish with freshly cracked black pepper

📦 Storage & Conservation

Store leftover casserole in an airtight container in the refrigerator for up to 3 days

Reheat covered in a 350F oven until warmed through, about 20 minutes

Freeze portions in freezer-safe containers for up to 2 months

Let frozen portions thaw overnight in the refrigerator before reheating

♻️ Leftover Ideas

Use leftover casserole as a savory pie filling

Blend with stock for a creamy onion soup

Serve over pasta for a quick meal

Mix into scrambled eggs for a decadent breakfast

⚠️ Common Mistakes to Avoid

Not browning the butter long enough to develop its nutty flavor

Overcrowding the onions in the casserole dish, which prevents proper cooking

Adding cold cream to the brown butter sauce, which can cause separation

Skipping the resting period, resulting in a runny sauce

FAQ

Can I use regular onions instead of pearl onions? ▶

While possible, pearl onions provide the best texture and presentation for this dish

How do I know when the butter is perfectly browned? ▶

Look for a golden brown color and nutty aroma, with brown bits forming at the bottom of the pan

Can I make this ahead of time? ▶

Yes, assemble up to 24 hours in advance and bake just before serving

Why did my sauce separate? ▶

This usually happens when ingredients are at different temperatures or the sauce is heated too quickly

How do I prevent the top from burning? ▶

Monitor closely and cover with foil if browning too quickly

Reviews

Sarah M.

⭐⭐⭐⭐⭐

Feb 4, 2026

The brown butter sage combination is absolutely divine! Best casserole I've ever made.

Michael P.

⭐⭐⭐⭐☆

Jan 16, 2026

Delicious but time-consuming to prepare. Worth the effort though!

Rachel B.

⭐⭐⭐⭐⭐

Feb 4, 2026

Those pearl onions become incredibly sweet and tender. Amazing recipe!

David K.

⭐⭐⭐☆☆

Feb 8, 2026

Good flavor but sauce was a bit rich for my taste.

Emma T.

⭐⭐⭐⭐⭐

Feb 11, 2026

Perfect side dish for Thanksgiving! Everyone wanted the recipe.