Combine the chocolate and 3 tablespoons butter in a heat-safe bowl set over simmering water. Cook, stirring occasionally, until melted and smooth.

In a medium bowl, combine 3 tablespoons sugar, egg, egg yolk, vanilla, and salt. Whisk until thick and pale, about 2 minutes. Whisk in flour until smooth.

Gently stir chocolate mixture into egg mixture.

Pour the mixture into the ramekin. Bake for 12 to 14 minutes until the edges are set and puffed, but the center is still soft.

Loosen the edges and invert onto a plate. Dust with confectioners’ sugar and serve with ice cream or whipped cream.