Christensen's Cafe Chocolate Birthday Cake

Why I Love This Recipe
My grandfather and grandmother, Oscar and Cassie Christensen owned a little cafe in a small town in Iowa. They had many great recipes for old-fashioned comfort food, but one of my favorites was this chocolate cake recipe. I make it for all my family's birthdays.
Ingredients You'll Need
Cake:
2 squares unsweetened chocolate
1 1/2 cups sugar
1 1/2 cups water
1/2 cup butter (scant)
2 eggs, separated
2 cups flour
2 tsp. baking powder
2 tsp. salt
1 tsp. soda
1 tsp. vanilla
1 tsp. vinegar
Frosting:
4 cups powdered sugar
7 Tbsp. milk
Dash of salt
3 Tbsp. butter
2 squares unsweetened chocolate
Directions
Cake:
Prepare two 8 inch round cake pans by lining with Reynolds Parchment Paper.
Melt chocolate, 1/2 cup sugar and 1/2 cup water.
Add 1 cup cold water to this mixture and cool.
Cream remaining sugar, butter and egg yolks.
In a small bowl, mix flour, baking powder, salt and soda.
Add dry ingredients alternately with chocolate mixture to sugar and butter mixture.
Add vanilla and vinegar.
Beat egg whites stiffly and fold in.
Pour cake batter evenly into the two cake pans.
Bake at 350 degrees for 25 minutes or until toothpick inserted in middle comes out clean.
Cool cakes on cooling rack.
Remove from cake pans and frost.
Frosting:
Add milk to sugar. Melt butter and chocolate squares and add to sugar mixture. Beat until of spreading texture and frost cakes.