Mix 1 teaspoon flour and cocoa powder together in a bowl.
Preheat oven to 350 degrees F (175 degrees C). Butter 6 metal pudding ramekins and use a fine sieve to dust the insides with the flour-cocoa powder mixture.
Place chocolate and 1/3 cup plus 2 tablespoons butter in a heatproof bowl and set over a saucepan of boiling water. Stir until melted, 3 to 5 minutes. Remove bowl from the saucepan and set aside to cool slightly.
Whisk egg yolks and sugar together in a bowl until light and fluffy. Whisk in 1/3 cup plus 2 tablespoons flour gradually until smooth. Stir in the cooled melted chocolate-butter mixture.
Whisk egg whites together in a bowl, using a clean whisk, until stiff. Fold gently into the chocolate-butter mixture. Pour into the prepared ramekins.
Bake in the preheated oven until risen but slightly undercooked inside, 6 to 8 minutes.
Carefully remove ramekins from the oven and loosen the sides of each cake with a round-bladed knife.
