1. Place chopped chocolate or chocolate chips in a large heatproof (glass or metal) bowl, set over a saucepan of simmering water. Gently melt, stirring to dissolve the solid pieces.
2. Once all chocolate has melted, remove bowl from heat and stir in melted butter.
3. Whisk in sugar and eggs.
4. Stir in sifted cocoa powder.
5. Transfer batter into well-greased ramekins or cake pan lined with foil and sprayed with non-stick spray.
6. Place in oven at 375F for 25 minutes.
7. Garnish with icing sugar and serve warm with vanilla ice cream.