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Brussels Sprouts Gratin in a casserole dish
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5 from 2 votes

Brussels Sprouts Gratin

This brussels sprouts gratin with cheese sauce is based on Julia Child's Choux de Bruxelles à la Mornay, Gratinés, and is a rich vegetable side dish made with homemade béchamel.
Prep Time5 minutes
Cook Time20 minutes
Total Time25 minutes
Course: Side Dish
Cuisine: French
Diet: Gluten Free, Vegetarian
Servings: 6 people
Calories: 235kcal

Equipment

  • medium casserole dish (9"x9" or 10"x10")
  • heavy-bottomed pan

Ingredients

Brussels Sprouts:

  • 1 ½ pounds brussels sprouts, stems removed + sprouts halved or quartered
  • 2 tablespoons olive oil Or swap 2 TB melted butter
  • ¼ teaspoon sea salt

Béchamel Sauce:

  • 2 cups milk
  • 3 tablespoons butter, divided
  • 2 tablespoons flour Use AP gluten-free flour if needed
  • ½ cup freshly grated Swiss (esp. Gruyere) or Parmesan cheese, divided Or use a mixture of both cheeses
  • ¼ teaspoon sea salt
  • ¼ teaspoon ground cayenne
  • ¼ teaspoon freshly ground nutmeg

Instructions

  • Preheat oven to 425°F.
    Toss brussels sprouts with olive oil and sea salt. Arrange in a medium casserole dish (9x9 or 10x10), and bake 14-15 minutes, or until the sprouts have just turned bright green.
    Toss Brussels Sprouts with Oil + Salt
  • While sprouts cook, make the béchamel sauce.
    Bring the milk to a boil in a saucepan. Alternatively, microwave the milk until it begins to simmer.
    Heat 2 tablespoons butter in a heavy bottomed pan over low heat. When the butter melts, stir in the flour. Continue stirring until the flour is incorporated with the butter and they begin to foam (but not brown). Allow the mixture to foam for 2 minutes.
    Begin slowly pouring in the hot milk, stirring or whisking constantly. The milk should be very hot (almost at boiling) when you pour it into the butter and flour.
    Bring the mixture to a boil and continue to boil for 1 minute. Turn off the heat.
    Stir in Hot Milk
  • Stir ¼ cup of the cheese into the béchamel, and continue stirring until the cheese is melted.
    Add the sea salt, cayenne, and nutmeg. Stir again, and then taste. Add more seasoning if desired.
    Season the Add Cheese to the Béchamel
  • When the sprouts are done roasting, fold half the sauce into the sprouts and stir.
    Pour the remaining sauce over the sprouts. Top with the remaining cheese.
    Cut the remaining butter into small cubes and dot the top.
    Mix Sauce with Sprouts + Top with Cheese
  • Move an oven rack to the position closest to the broiler.
    Position the casserole dish under the broiler and broil 3-5 minutes, or until the cheese is golden and bubbling.
    Serve immediately.
    Broil Until Golden

Notes

Partially Make Ahead:  This dish tastes best right after cooking, but can be partially prepped ahead.
  • Prepare the raw brussels sprouts by trimming and halving (or quartering) and store in the fridge for up to two days.
  • Prepare the béchamel sauce up to three days ahead and store in the fridge.  Reheat over low heat, adding more hot milk if needed.
For more tender brussels sprouts: Blanch in boiling water for 6-8 minutes before roasting. 
Béchamel troubleshooting:
  • My sauce is lumpy: If the milk is still almost boiling when added and if you stir or whisk vigorously, there shouldn't be lumps.  If there are, you can purée the sauce in a blender.
  • The sauce is too thick: With the heat on, whisk a little more hot milk back into the sauce.  (Gluten-free AP flour will sometimes thicken the sauce more than intended.)  Note that extra-thick sauce will work fine in this recipe, just make sure to spread it out evenly over the sprouts.

Nutrition

Calories: 235kcal | Carbohydrates: 17g | Protein: 9g | Fat: 16g | Saturated Fat: 8g | Cholesterol: 32mg | Sodium: 325mg | Potassium: 555mg | Fiber: 4g | Sugar: 7g | Vitamin A: 1270IU | Vitamin C: 96mg | Calcium: 212mg | Iron: 2mg