Chocolate Swirl Babka
From Jewish Cooking in America by Joan Nathan

Serves 12

Dough:
1/3 cup milk
1 package active dry yeast
1/2 cup sugar
2 sticks (1 cup) unsalted butter
4 large egg yolks (reserve 2 whites for meringue)
4 cups sifted all-purpose flour
dash salt

Chocolate filling:
2 oz. good-quality bittersweet chocolate
1/4 cup sugar
1/2 stick (1/4 cup) butter
1/4 cup milk
1 tsp. vanilla

Meringue:
2 egg whites
1/4 cup sugar

Heat the milk to lukewarm and add the yeast with 1 teaspoon of the sugar. Stir until blended. Let sit 10 minutes or until the yeast starts to bubble.

Cut the butter into small bits. Place in a food processor or mixer and add the egg yolks and yeast mixture, blending well. Gradually add the flour, salt and remaining sugar, beating into a soft dough. Cover and leave in the refrigerator for 6 hours or overnight.

In the morning remove the dough from the refrigerator and leave at room temperature for 45 minutes.

To make the chocolate filling, melt the chocolate over a double boiler. Add the sugar, butter and milk. Heat in the double boiler about 15 minutes, stirring occasionally, until thickened. Add the vanilla and cool.

To make the meringue, bring the egg whites to room temperature and beat them with the sugar to make a stiff, but not dry, meringue.

Divide the dough in half. Sprinkle with flour. Knead the dough briefly and roll out into a rectangle about 1/8-inch thick. Spread with half the chocolate and then half the meringue. Roll up like a jellyroll and place in half of a greased tube pan. Repeat the process with the remaining dough, chocolate and meringue, fitting it in the other half of the pan. Pinch the ends together to form a circle. Don't worry if some of the filling oozes out.

Cover with a towel and let rise 1 hour.

Bake 35-45 minutes in a preheated 350-degree oven. Cool about 30 minutes in the pan, remove and serve.