01 - Preheat oven to 400°F. Butter four 7 oz ramekins and dust generously with sugar, tapping out the excess.
02 - In a heatproof bowl, melt the chocolate and butter over a pot of barely simmering water (double boiler method), stirring until smooth. Remove from heat and let cool slightly.
03 - In a medium bowl, whisk together the egg yolks, 1/4 cup sugar, vanilla extract, and salt until pale and creamy. Stir in the melted chocolate mixture and flour until fully combined.
04 - In a clean, dry bowl, beat egg whites until soft peaks form. Gradually add a pinch of sugar and continue beating until stiff, glossy peaks form.
05 - Gently fold one-third of the whipped egg whites into the chocolate mixture to lighten it. Then fold in the remaining whites carefully, maintaining as much air as possible.
06 - Spoon the batter into the prepared ramekins, smoothing the tops. Run your thumb around the inside edge of each ramekin to help the soufflés rise evenly.
07 - Bake for 16-18 minutes, until the soufflés are well risen with a slight wobble in the center.
08 - While the soufflés bake, prepare the crème anglaise: In a saucepan, heat milk, cream, and split vanilla bean (or extract) over medium heat until just below simmering.
09 - In a bowl, whisk egg yolks and 1/4 cup sugar until pale. Gradually pour the hot milk mixture into the yolks, whisking constantly.
10 - Return the mixture to the saucepan and cook over low heat, stirring constantly with a wooden spoon, until it thickens enough to coat the back of the spoon (do not let it boil). Strain into a bowl. Remove vanilla bean if used.
11 - Serve the soufflés immediately out of the oven, with crème anglaise poured over or served alongside.