Preheat oven to 325 °F.

Generously grease 9-inch springform pan with 1-3/4-inch high sides with butter. Dust with flour. Invert and shake out excess flour.

Sift together cake flour, cocoa powder, baking powder, soda, salt. Set aside.

Using electric mixer, beat 1-1/3 cups sugar, butter, 3 egg yolks, and 1 whole egg until blended..

Beat in flour mixture alternately with buttermilk in 3 additions.

Mix in chocolate chips.

Using clean dry beaters and a dry bowl, beat 3 egg whites until soft peaks form. Gradually add rest of sugar, beating until stif glossy peaks form — about 5 minutes.

Spread 2/3 of meringue halfway up sides (not bottom) of prepared pan.

Spoon batter into meringue-lined pan; top with remaining meringue by dropping in large spoonfuls in a single layer on top of chocolate batter. Using tip of knife, swirl top meringue and some of chocolate batter together.

Bake 80 to 85 minutes. Cool 10 minutes on rack.

Release pan sides. Cool completely.