Melt butter in a medium saucepan. Add cocoa and mix well. Remove from heat. Stir in sugar. Add vanilla, then stir in eggs, being sure mixture has cooled enough so that eggs don't cook, but instead mix in well. Stir in flour.
Drop dough by teaspoons-full onto hot waffle iron. You can make 4 at a time. Close waffle iron and let bake for 1 minute. Remove to wire racks to cool.
Frost with chocolate frosting and top with a pecan, if desired.
If you prefer not to frost cookies you can sprinkle with with powdeed sugar to finish.