My Onion Gratin is a great universal side dish ~ thick slices of onion bake up in a cheesy sauce finished off with a crunchy herb crumb topping ~ ready to set down next to a juicy steak, roast chicken, or grilled salmon dinner.
From shallots and green onions, to leeks, Vidalias, Maui, and just plain old reds, I’m always looking for ways to cast onions in the leading role, rather than burying them in the first few steps of a recipe. Onions are cheap and healthy, and so good tasting, they deserve better. Red onion gratin is a simple side dish that’s fancy enough for company, and goes with just about any meat, chicken or fish. I’d say it’s absolutely made to have with a great steak.
ingredients for onion gratin
- onions
- I used all red onions, but you can easily use white, or a mix. Sweet onions like Vidalia or Maui would be great, too.
- butter & flour
- make a roux for the base of the béchamel sauce.
- heavy cream
- don’t try to substitute something lighter like half and half, or your béchamel sauce may curdle when you add the sherry.
- thyme
- nutmeg
- want a real treat? Grate it fresh!
- sherry
- adds flavor, but can be omitted if needed. You can substitute a dry white wine or a dry Vermouth, or just use broth or stock.
- gruyere
- you can substitute a good sharp cheddar, too.
- breadcrumbs
- use store bought or homemade! I look for crumbs with a good, rustic texture to give the onion gratin the best crunch.
the secrets to perfectly cooked onion gratin
I pre-cook the thick onion slices a bit on a hot grill pan. The quick grilling not only gives them extra smokey flavor, but it softens them a little so they don’t need as much time in the oven.
I lay out my beautiful grilled slices over a basic sherry and nutmeg laced béchamel cream sauce, and then cover it all with shredded Gruyere and fresh breadcrumbs.
Slide the pan into the oven and in about 25 minutes or so you’ll pull out a gorgeous golden browned and bubbling side dish in the French fashion. So delicious, so elegant, and so easy!
how to make fresh breadcrumbs at home
I used a mixture of local store-brand breadcrumbs and panko-style breadcrumbs for extra texture. But for a really luxurious onion gratin, consider making your own breadcrumbs at home. It’s an easy and rewarding kitchen project ~ check out my post for the full how-to. You can use almost any kind of bread you want, and even add your own seasoning for an extra layer of flavor.
menu ideas for onion gratin
- Strip Steak
- Ribeye Steak
- Bourbon Glazed Meatloaf
- Instant Pot Pork Chops in Creamy Mushroom Sauce
- Ina Garten’s Mustard Chicken
- Creamy Lemon Dill Salmon
- Roast Chicken Breasts with Tarragon and Mustard Sauce
Onion Gratin
Equipment
- cast iron skillet or other oven ready skillet
Ingredients
- 2-3 large red onions
- olive oil for brushing
- 2 Tbsp unsalted butter, divided
- 1 Tbsp all purpose flour
- 2/3 cups heavy cream
- 3 Tbsp dry sherry
- salt and fresh cracked black pepper
- dash of nutmeg, I grate mine fresh
- handful of fresh thyme
- 1 cup shredded Gruyere cheese
- 2/3 cup breadcrumbs
Instructions
- Preheat oven to 400F
- Peel and thickly slice the onions about 1/2" thick. If you cut them much thicker than that, you may have trouble getting them cooked through.
- Heat a grill pan until quite hot, and brush the onion slices lightly with olive oil. Grill the slices for a minute or two on each side so that they get slightly softened and have nice grill marks. Set them aside.
- In a saucepan, heat 1 Tbsp of the butter over medium heat, and stir in the flour. Cook for a minute, stirring constantly. Pour in the cream and sherry and whisk until smooth. Stir constantly while the mixture comes up to a simmer and is thickened. Add salt and pepper to taste and the dash of nutmeg.
- Pour the sauce into a cast iron skillet or gratin dish. Arrange the onion slices over the sauce.
- Sprinkle the cheese evenly over all.
- Stir the breadcrumbs together with the last tablespoon of melted butter, and a little salt, pepper, and a few thyme leaves. Sprinkle the breadcrumbs over the cheese,
- Bake for about 20-25 minutes until browned and bubbling. Check the onions with the tip of a sharp knife, they should feel tender. You can run the gratin under the broiler at the last minute if you want extra browning,
Can this be frozen
Yes, you can freeze it.
I’ve tried various gratins but never one with onions – love!
love this idea… such a novel way to prep onions… very pretty x
I could stick my whole face in that! Looks scrumptious!!
Of course, why not? An onion gratin! So perfect!
I love the idea of elevating the humble onion to a much over-looked, but well deserved, side dish status.
Yum for dinner in my book with anything… even a toasted slice of hearty bread.
Great photos.