Shrimp Au Gratin Recipe

Prepare shrimp

Pat the shrimp dry with paper towels and season lightly with 1/4 tsp of the salt and 1/4 tsp of the pepper.

Sauté mushrooms

Heat a large skillet over medium-high heat. Add 1 tbsp (1 tsp olive oil + 2 tsp butter alternative included in butter total) of butter/oil to the pan. Add sliced mushrooms and a pinch of salt and cook, stirring occasionally, until they release their juices and begin to brown, about 6–8 minutes. Transfer mushrooms to a bowl and set aside.

Cook shrimp

Reduce heat to medium, add remaining 1 tbsp butter to the skillet. Add minced shallot and cook 1–2 minutes until softened. Add garlic and cook 30 seconds until aromatic. Add seasoned shrimp in a single layer and cook 1–2 minutes per side until just opaque (shrimp will finish cooking in the oven). Remove shrimp to the bowl with mushrooms and set aside; reserve pan juices in the skillet.

Make roux

With the skillet still over medium heat and pan juices present, add 1 tbsp butter and melt. Sprinkle the 1 tbsp flour over the melted butter and whisk continuously for 1 minute to cook the raw flour taste.

Build sauce

Slowly whisk in the 3 tbsp milk to form a smooth paste, then whisk in the heavy cream and the 2 tbsp white wine (if using). Bring the mixture to a gentle simmer, stirring frequently, until it thickens slightly, about 3–4 minutes.

Finish sauce

Reduce heat to low. Whisk in Dijon mustard, the pinch of nutmeg, remaining salt and pepper amounts (to total 1 tsp each), then stir in grated Gruyère and 1 oz Parmesan a handful at a time until smooth and fully melted. Taste and adjust seasoning. If sauce becomes too thick, whisk in up to 1–2 tbsp additional cream or milk to reach a spoon-coating consistency.

Preheat oven to 400°F (200°C). Lightly butter or oil four 6–8 oz gratin dishes or one shallow 9x9-inch baking dish.

Return the cooked shrimp and mushrooms to the skillet with the cheese sauce and gently fold to coat evenly. Add chopped parsley and stir to combine.

Spoon the shrimp-mushroom mixture into the prepared dishes, dividing evenly.

Combine the 1 tbsp panko with 1 tbsp grated Parmesan and 1 tsp olive oil or melted butter; sprinkle evenly over each gratin. Add an extra light dusting of Parmesan if desired.

Bake in the preheated oven until the topping is golden and the filling is bubbling, about 10–12 minutes. If you want a crispier, browned top, place under broiler for 1–2 minutes — watch closely to avoid burning.

Remove from oven and let rest 3–5 minutes. Spoon a squeeze of lemon over each portion to brighten flavors and garnish with chopped chives or parsley before serving.