Melt the chocolate chips and butter over a double boiler until melted and smooth. Remove from the heat.
Place the water and granulated sugar into a heavy, small saucepan. Stir just to combine. Boil over medium high heat until a candy thermometer reads 240 degrees. Be patient. This can take about 6-8 minutes.
In the bowl of an electric mixer, using the whip attachment, beat the egg whites at medium high speed until soft peaks form.
While on medium high speed, slowly pour the boiling sugar syrup into the egg whites pouring against the side of the mixing bowl and not directly onto the whip. Increase the mixer speed to high and beat until the mixture forms stiff peaks.
On low speed add the melted chocolate and blend well. Remove the bowl from the motor and using a rubber spatula finish blending in the chocolate that may be on the bottom of the mixing bowl. Pour the mixture into a large bowl.
Clean and dry the bowl of the electric mixer, and using the cleaned whip attachment, beat the heavy cream at high speed until soft peaks have formed. Add the vanilla extract and beat until stiff peaks form and the vanilla is incorporated.
Transfer the whipped cream on top of the chocolate meringue mixture and using a rubber spatula, fold the two together until almost no streaks remain. Cover the bowl with plastic wrap and chill for several hours or overnight.