Heat oven to 350ºF. Grease (spray) a mini muffin tin (24 cups).
In a heatproof bowl, melt butter and chocolate in the microwave for about 2 minutes, stir using a whisk halfway through. Whisk until smooth.
Whisk in cocoa, set aside.
In a separate bowl, whisk together eggs, sugar, vanilla and salt.
Whisk in the cocoa mixture.
Using a spatula or wooden spoon, stir in the flour until just combined.
Spoon into mini-muffin tin, almost ‘till the top. You may have a little extra; when I do, I like to put the batter in heat proof espresso cups or tea cups (sprayed), and then I put the cups on a little cookie sheet (from the toaster oven), in the oven beside the muffin tray.
Bake for 15-17 minutes.
