Green Bean Au Gratin

5 from 4 votes

Green Bean Au Gratin is the perfect vegetable side dish for your holiday table! An all around better version of green bean casserole, with no condensed soup or mushy canned green beans! This elegant dish starts with caramelized onions and garlic in a creamy milk sauce, made easy with frozen green beans, and baked with a cheesy bread crumb crust!

Prep Time5

Cook Time50

Total Time55

Course: Side Dish

Cuisine: French

Servings:

Calories: 415kcal

Author: Meryl Downing

Ingredients

4 Tablespoons butter
1 onion sliced
½ teaspoon kosher salt
8 grinds fresh black pepper
3 cloves garlic minced
4 Tablespoons flour
2 cups milk
½ teaspoon dried or fresh thyme
⅛ teaspoon nutmeg
20 ounces frozen green beans (about 4 to 5 cups)
2 cups white cheddar cheese shredded, divided
½ cup Parmesan cheese shredded, divided
1 Tablespoon butter
½ cup bread crumbs

Instructions

In a large skillet over medium low heat, melt 4 Tablespoons of butter and caramelize the sliced onions. This is a slow process, about 10 to 15 minutes, stirring often until golden brown. They should sizzle gently, turn the heat down if they begin to burn! Pre-measure your salt and pepper and add a pinch to the onions.
When the onions are golden and caramelized, add the garlic and flour and cook another minute to incorporate. This will form a roux, the thickener for the sauce.
Add the milk, thyme, nutmeg and the rest of the salt and pepper. Whisk together over medium low heat until thickened, about 5 minutes.
When the sauce has thickened, add the frozen green beans (no need to thaw) and half the cheese. Mix well.
Transfer to a baking dish and smooth the top, it will be very thick. Cover with the rest of the cheese. Melt 1 Tablespoon of butter and toss with the bread crumbs and sprinkle over the top.
Bake at 400℉ for about 30 minutes until golden and bubbly. You can broil it a few minutes to get the top a golden brown.

Notes

Baking Dish - I used an 8x8 square baking dish. You can dump your frozen green beans into the dish to eyeball the right size to use. You can double the recipe for a larger group.
Bread Crumbs - Use store-bought panko bread crumbs or make your own by pulsing a chopped bun or any bread from your freezer in the food processor! Avoid the regular, completely powdery breadcrumbs. They won't give you the right texture.
Milk - Whole milk is best, but 2% is fine. If all you have is skim, you may want to add a splash of cream or sub a bit with half & half.
Green Beans - I used two 10 ounce bags of cut frozen green beans. You can also use blanched and frozen green beans from your summer garden, just measure out 4 cups.
If using fresh green beans, blanch them first in boiling salted water for about 3 minutes. Don't use overgrown large fibrous green beans. Their texture is terrible, no matter how long you cook them!

Nutrition