This is not just a chocolate cake, it is a CHOCOLATE cake. Deeply, densely and INTENSELY chocolate. I was in a hurry to make this for a party so the photos are not great but I had to share. From Bon Apetit 2006. This is gluten free.  

INGREDIENTS

Cake
1 cup water
3/4 cup sugar
9 tablespoons (1 stick plus 1 tablespoon) unsalted butter, diced
18 ounces semisweet chocolate, chopped
6 large eggs

Ganache
1 cup heavy whipping cream
2 tablespoons creamy peanut butter (optional)

Additions
2 tablespoons Chambord Liquor (optional)
8 ounces semisweet chocolate, chopped

PREPARATION

For cake:
Preheat oven to 350°F. Butter 10-inch-diameter springform pan. Line bottom of pan with parchment round; butter parchment. Wrap 2 layers of heavy-duty foil around outside of pan, bringing foil to top of rim. Combine 1 cup water and sugar in small saucepan. Bring to boil over medium heat, stirring until sugar dissolves. Simmer 5 minutes. Remove from heat.

Melt butter in large saucepan over low heat. Add chocolate and whisk until smooth. Whisk sugar syrup into chocolate; cool slightly. Add eggs to chocolate mixture and whisk until well blended. Pour batter into prepared pan. Place cake pan in large roasting pan. Add enough hot water to roasting pan to come halfway up sides of cake pan.

Bake cake until center no longer moves when pan is gently shaken, about 50 minutes. Remove from water bath; transfer to rack. Cool completely in pan.

For ganache:
Bring whipping cream to simmer in small saucepan over medium heat. Remove from heat. Add chocolate and whisk until smooth. Add the peanut butter or liquor if you desire. Pour over top of cake still in pan. Gently shake pan to distribute ganache evenly over top of cake. Refrigerate cake in pan until ganache is set, about 2 hours. DO AHEAD: Can be made 2 days ahead. Cover and keep refrigerated.

Run knife around pan sides to loosen cake; release sides. Cut cake into wedges.