"This will impress any guests you entertain and you don't have to tell them how easy it was! Serve with chocolate ganache and raspberry sauce. I used recipes I found here on Allrecipes.com for chocolate ganache (by INGRIDEVOGEL) and raspberry sauce (by The_Tattooed_Chef). The raspberry sauce complements all that chocolate and makes the cake moist. Both of these recipes are easy, simple, and exceptional as well."
Preheat oven to 325 degrees F (165 degrees C). Grease a 10-inch cake pan with oil.
Combine chocolate, butter, and sugar in a double boiler over simmering water; cook, stirring frequently and scraping down the sides with a rubber spatula, until melted and smooth, about 5 minutes.
Pour chocolate mixture into the bowl of a stand mixer fitted with the paddle attachment; beat on low speed until cooled, about 5 minutes. Increase speed to medium; beat in eggs one at a time. Add water and vanilla extract; beat on low speed until blended. Pour into the prepared pan.
Place cake pan inside a large baking dish. Pour enough water into the baking dish to come halfway up the sides of the cake pan.
Bake cake in the preheated oven until a knife inserted into the center comes out clean, about 1 hour. Allow cake to cool in the water bath, about 1 hour. Transfer to the refrigerator; chill until firm, 8 hours to overnight.