Whip the egg yolks until creamy and gradually stir in 200 g of sugar. Add lemon juice and grated lemon zest. Beat the egg whites until stiff and fold carefully into the egg yolk mixture.
Spread the mixture on 4 molds spread with melted butter and sprinkled with sugar and cook in a water bath for 30 minutes.
For the sauce, melt the sugar and caramelize it lightly. Add orange, lemon juice and orange liqueur and let it boil down, add the butter. Pour boiling water over the orange peel, then cut into thin strips and garnish the lemon mousse with it