This is my Mother-In-Law’s recipe. It is absolutely delicious. I will post her Chocolate cake next. 
SHANA’S MARBLE CAKE
1/2 Cup Shortening
1 Stick Butter
1 3/4 Cup Sugar
4 Eggs
3 Cups Cake Flour
3 tspsBaking Powder
1 Cup Milk
2 tsps Vanilla
6 ozs Semi-sweet Chocolate Chips
Preheat oven to 350*
Melt 6ozs chocolate chips with 4 Tbsps water and let cool.
Sift flour and baking powder together twice.
Beat butter, shortening & sugar together. Add eggs one at a time. Alternate adding flour and milk, starting and ending with flour. Add vanilla. Take out one cup batter and add melted chocolate mixture to it. Grease and flour a tube pan. Pour 1/2 white batter into pan and spread evenly. Pour chocolate batter into the pan and spread carefully. Then add remaining white batter to pan. Take a butter knife and swirl it around the batter to marble.
Bake for 50 to 60 minutes, testing with a toothpick after 50 minutes. Cake is done when the toothpick comes out clean.
ENJOY