Field Pea Gratin Recipe

Sweat onions

Melt 2 tablespoons butter in a medium saucepan over medium-low heat. Add the thinly sliced spring onions and the minced shallot (if using). Season lightly with a pinch of salt. Cook gently, stirring occasionally, until very soft and translucent but not browned, about 10–12 minutes.

Build soubise

Stir in 1 tablespoon flour and cook for 1 minute to remove the raw flour taste. Slowly add 1/2 cup warm stock, stirring constantly to make a smooth slurry. Bring to a gentle simmer and cook 2–3 minutes until slightly thickened.

Finish soubise

Reduce heat to low and stir in 1/2 cup heavy cream. Simmer very gently for 3–4 minutes until the mixture is creamy. Season with 1/2 teaspoon salt, 1/4 teaspoon white pepper, and 1 teaspoon lemon juice. Taste and adjust seasoning. If a very smooth texture is desired, cool slightly then purée with an immersion blender or in a food processor until silky; return to low heat to warm before assembling. Keep warm while preparing the gratin.

Prepare peas

If using frozen peas, place 3 cups in a colander and run under warm water to thaw, then drain thoroughly. If using fresh peas, blanch in boiling salted water for 2 minutes, then shock in an ice bath and drain. Pat dry.

Make béchamel

In a medium saucepan melt 2 tablespoons butter over medium heat. Whisk in 2 tablespoons flour and cook, whisking constantly, for 1–2 minutes without browning. Gradually whisk in 1 1/2 cups whole milk and 1/2 cup heavy cream, bringing to a gentle simmer. Cook, stirring, until the sauce is thick enough to coat the back of a spoon, about 4–6 minutes. Season with 1 teaspoon salt, 1/2 teaspoon freshly ground black pepper, and 1 teaspoon lemon zest.

Combine with peas

Remove the béchamel from heat. Stir in 1 cup of grated gruyère into the sauce until melted, reserving about 1/2 cup for the top. Fold the prepared peas into the cheesy béchamel until evenly coated. Taste and adjust seasoning.

Assemble gratin

Preheat oven to 375°F (190°C). Butter a shallow 8-inch gratin or baking dish with 1 teaspoon butter. Spoon half of the warm spring onion soubise evenly into the bottom of the dish. Spread the pea and béchamel mixture over the soubise, then dollop or gently spread the remaining soubise over the peas (you want some green peeking through). Smooth the surface and sprinkle the reserved 1/2 cup gruyère and 1/4 cup grated parmesan evenly over the top.

Optional crunchy topping

If using panko, toss 1/2 cup panko breadcrumbs with 1 teaspoon olive oil or melted butter and sprinkle over the cheese for extra crunch.

Bake

Place the gratin in the preheated oven and bake until the top is golden and bubbling, about 20–25 minutes. If the top browns too quickly, tent loosely with foil. For a deeply browned crust, finish under a hot broiler 1–2 minutes — watch carefully to avoid burning.

Rest

Remove from oven and let rest 5 minutes so the sauce settles.

Sprinkle 2 tablespoons chopped chives over the gratin and garnish with microgreens or pea shoots if using. Serve warm, portioned into 4 servings. The spring onion soubise layered under and over the peas gives a sweet, oniony creaminess that complements the nutty gruyère.