Adapted from the Cook’s Illustrated Best Recipe cookbook.
8 tablespoons (1 stick) unsalted butter, plus extra for ramekins
8 ounces bittersweet chocolate (I use Ghirardelli 60% cacao bittersweet chocolate chips; chocolate with a lower cacao content won’t taste as good)
4 large eggs plus 1 large yolk, at room temperature
1 teaspoon vanilla extract
Generous ¼ teaspoon coarse sea salt
½ cup sugar
2 tablespoons all-purpose flour, plus extra for ramekins
Whipped cream or vanilla ice cream for serving
1. Adjust the oven rack to the center position and preheat to 400 degrees.
2. Generously butter and flour eight 6-ounce ramekins or Pyrex custard/baking cups; tap out excess flour and position ramekins on a shallow pan or baking sheet with sides.
3. Melt 8 tablespoons butter and chocolate in heatproof bowl set over a pan of almost-simmering water, stirring once or twice until smooth; remove from heat.
Heat chocolate alone at 50 percent power for 2 minutes; stir, and add butter. Continue heating at 50 percent for another 2 minutes, stopping to stir after 1 minute. If chocolate is not yet entirely melted, heat an additional 30 seconds at 50 percent power.
4. Beat eggs, yolk, vanilla, salt and sugar at highest speed in bowl of standing mixer fitted with the whisk attachment until the volume nearly triples, color is very light, and mixture drops from beaters in a smooth, thick stream, about 5 minutes.
Beat for 10 minutes using a handheld mixer and large mixing bowl.
5. Transfer chocolate to a large bowl. Scrape egg mixture over melted chocolate and butter; sprinkle flour over egg mixture. Gently fold egg and flour into chocolate until mixture is uniformly colored. Ladle or pour batter into prepared ramekins. (Can be covered lightly with plastic wrap and refrigerated up to 8 hours. Rest at room temperature for 30 minutes before baking.)
6. Bake until cakes have puffed about ½ inch above rims of ramekins, have a thin crust on top, and jiggle slightly at center when ramekins are shaken very gently; 12 to 13 minutes.
7. Run a paring knife around inside edges of ramekins to loosen cakes and invert onto serving plates; cool for 1 minute and life off ramekins. Serve immediately with whipped cream, ice cream, or a good glass of red wine.
8. Accept accolades and enjoy!