French Chocolate Mousse - cooking recipe

Ingredients

4 egg yolks
3/4 c. sugar
1/4 c. orange liqueur
1 c. semi-sweet chocolate pieces
1 tsp. instant coffee, dissolved in 1/4 c. cold water
1/2 c. soft butter or margarine
1/4 c. finely chopped candied orange peel
4 egg whites
1/4 tsp. salt
1 Tbsp. sugar

Preparation

In top of double boiler, beat egg yolks and sugar with electric or rotary beater until thick and lemon colored.
Beat in orange liqueur.
Cook over hot, not boiling, water.
Beat constantly, just until hot and mixture thickens slightly (about 10 minutes).
Transfer top of double boiler to pan of cold water and beat until consistency of mayonnaise, 4 or 5 minutes.