Heat a waffle iron (Belgian or regular). In a medium bowl, whisk together the butter, sugar, eggs and vanilla until smooth. Stir in cocoa, flour and salt until just combined. One at a time, drop a large spoonful of batter onto the hot waffle iron and cook for 30-60 seconds, just until the cookie is baked through and can be removed carefully by gently lifting one edge. Don't overbake or the cookies will be dry!
Serve warm with a scoop of ice cream or serve at room temperature with whipped cream and berries - really, the possibilities are endless.
Store leftover cookies in a ziploc bag so they stay soft.
Notes
Size: the size of these cookies is completely dependent on how big you make them in the waffle iron. I got about 8 - they were the perfect size for a scoop of ice cream.