Purple sprouting broccoli gratin with cheese sauce and toasted brioche

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I spent three years making broccoli gratins that tasted like they'd been through a blender — the cheese sauce was either too thick or curdled into something unrecognizable. This version finally clicked after I stopped trying to be clever and just let the ingredients do what they're good at: purple sprouting broccoli has this tender sweetness, Gruyère melts without breaking apart, and toasted brioche adds a crunch that doesn't go stale before dinner is done.

I make it when I want something that feels special but doesn't require standing over a stove. The cooking happens mostly in the oven while I handle whatever else needs doing. A trick I keep coming back to: don't skip blanching the broccoli first. Even five minutes under boiling water means the florets cook evenly with the sauce, and you won't end up with raw stems or mushy tops.

Leftovers keep well for three days in the fridge. I reheat them on a sheet pan at 375°F so the top crisps back up instead of turning rubbery — worth the extra ten minutes if you're feeding more than two people.

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Prep Time 20

Cook Time 35

Total Time 55

Servings: 6 servings

Course: Side Dish

Cuisine: American

Calories: 480

Ingredients Method Nutrition

Ingredients

For the cheese sauce

4 tbsp unsalted butter
¼ cup all-purpose flour
2 cups whole milk warmed
1½ cups Gruyère cheese freshly grated (about 6 oz)
1 cup sharp cheddar shredded
2 large egg yolks
1 tsp Dijon mustard
½ tsp smoked paprika
Kosher salt and fresh cracked black pepper

For the broccoli

1 lb purple sprouting broccoli stems trimmed to about 3 inches
2 tbsp olive oil
4 cloves garlic cloves thinly sliced
Pinch red pepper flakes optional

For assembly

6 slices brioche cut into ½-inch cubes (about 8 oz total)
3 tbsp unsalted butter melted
Extra grated Gruyère for topping
Fresh parsley or chives for garnish

Method

Blanch the broccoli: Bring a large pot of salted water to a rolling boil. Add the purple sprouting broccoli and cook for exactly 5 minutes until bright green and tender-crisp. Drain immediately, then spread on a baking sheet to cool slightly.
Make the sauce base: Melt butter in a medium saucepan over medium heat. Whisk in flour and cook for 1 minute until bubbly but not browned — this is your roux. Gradually whisk in the warm milk, stirring constantly, until smooth and thickened (about 3 minutes). Remove from heat.
Temper the eggs: Whisk egg yolks in a separate bowl. Slowly pour about ½ cup of the hot cheese sauce into the yolks while whisking vigorously. Pour this mixture back into the saucepan and stir well to prevent curdling.
Finish the sauce: Stir in both cheeses, Dijon mustard, smoked paprika, salt, and pepper until smooth. The sauce should coat a spoon thickly but still be pourable — if too thick, add 2-3 tbsp warm milk. Set aside.
Toast the brioche: Toss brioche cubes with melted butter on a baking sheet. Bake at 400°F for 8-10 minutes until golden and crispy on all sides.
Assemble: Spread blanched broccoli in an even layer in a greased 9x13 baking dish (or two smaller dishes). Pour cheese sauce over the top, making sure every piece is covered. Sprinkle with extra Gruyère and scattered garlic slices.
Bake: At 400°F for 25 minutes until bubbling at the edges and golden on top. Add toasted brioche in the last 3-4 minutes so they stay crunchy.
Rest and serve: Let stand 5 minutes before serving — this helps the sauce set slightly. Garnish with fresh herbs if using. Serve warm.

Nutrition

Calories: 480kcalCarbohydrates: 28gProtein: 24gFat: 32gSaturated Fat: 17gCholesterol: 145mgSodium: 680mgPotassium: 420mgFiber: 4gSugar: 6gVitamin A: 28IUVitamin C: 22mgCalcium: 380mgIron: 3mg

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