Banana Soufflé

Name: Banana Soufflé
Ingredients: 1 tablespoon butter, softened; 4 tablespoons granulated sugar (see Tip); 4 eggs; ½ teaspoon ground cinnamon; 2 ripe bananas, peeled and mashed (2/3 cup); ⅛ teaspoon cream of tartar; 1 to 3 tablespoons sugar-free chocolate-flavor syrup; 1 to 2 teaspoons powdered sugar (see Tips)