Creamy Scallop & Mushroom Gratin Recipe

Creamy Scallop & Mushroom Gratin Recipe
Ingredients for 4 portions:
2 tbsp unsalted butter
1/2 cup diced shallots
8 oz button mushrooms, sliced
salt and pepper to taste
1 cup white wine
1 pound sea scallops (about 3 scallops per person)
1/2 cup heavy cream
1 egg yolk
cayenne to taste
2 tsp minced tarragon
1 tsp lemon zest
1/4 cup grated Gruyère cheese
Broil on high, about 8-10 inches under the flame, until the scallops are hot, and the cheese is browned and bubbling....