Pirozhnoe Kartoshka

Name: Pirozhnoe Kartoshka
Prep time: 1 h
Cook time: 1 h
Total time: 2 h
Cuisine: European, Eastern European
Ingredients: 2 9-10 inch round sponge cakes; 1½ sticks butter, softened; ½ -3/4 can condensed milk; 3-4 oz bittersweet or unsweetened chocolate, melted and cooled; ¼ teaspoon salt; 2 teaspoons vanilla; 1 Tablespoon chocolate or hazelnut liqueur , optional