In a large bowl, whisk together sugar and eggs. In another bowl, whisk together flour, cocoa, and salt.
In a medium ovenproof nonstick skillet, bring butter and cream to a simmer over medium. Add chocolate; reduce to medium-low. Cook, stirring constantly, until chocolate has melted, about 1 minute. Remove from heat, and let cool 5 minutes.
Add chocolate mixture to sugar mixture, whisking until blended (reserve skillet)
Fold in flour mixture. Pour batter into skillet.
Bake until a toothpick inserted in center comes out clean, about 40 minutes.