Preheat oven to 350 degrees. Line 30 cupcake tins with paper or foil cupcake liners. In double boiler, set over medium heat, melt the 2/3 cup of chocolate chips, butter and vanilla. Stir until smooth. Remove from heat. Beat the eggs until frothy, using a whisk or electric mixer. Gradually, beat in the sugar until it dissolves. Gradually, beat in the flour. Fold in the chocolate mixture. Fill the cupcake tins 1/3 full with the chocolate batter. Mash together the cream cheese, sugar and egg until blended. Fold in the 1/2 cup of chocolate chips. Drop a heaping teaspoonful of filling into each cupcake. Cover cream cheese filling with another generous spoonful of batter. Bake for 25 to 30 minutes. Let cupcakes cool completely on a rack before storing in a covered container.