Pike Quenelles in Crayfish Sauce

Name: Pike Quenelles in Crayfish Sauce
Ingredients: 1 medium head of garlic, top fourth cut off; 2 tablespoons olive oil, divided; 1/2 cup unsalted butter (4 ounces); 2 quarts Lobster Stock (see Notes); 1/3 cup plus 2 teaspoon Cognac, divided; 4 cups heavy cream; 1 teaspoon ground piment d’Espelette; 1/2 teaspoon lemon juice; 1 tablespoons plus 3/4 teaspoon kosher salt, divided; 1 whole nutmeg; 10 ounces skinless pike or walleye fillet, cut into 1/4-inch pieces; 4 ounces sea scallops (about 3 large scallops), cut into 1/4-inch pieces; 4 large egg yolks; 1 large egg; 1/2 cup plus 2 tablespoons chilled unsalted butter (5 ounces), cut into 1/2-inch pieces and softened; 3/4 cup crème fraîche; 6 ounces small button mushrooms (about 2 cups); 6 ounces peeled cooked crayfish tails (about 1 1/2 cups); 8 whole cooked crayfish; Fresh flat-leaf parsley leaves, for garnish