• Pre-heat your oven to 180℃ Fan/390℉. Line a 12 hole muffin tin with muffin cases.
• In a small bowl, break up the dark chocolate and melt in the microwave in 20 second intervals, stirring in between to make sure it doesn't burn. Alternatively, set up a double boiler. Do this by placing a heatproof bowl over a small pot of simmering water. Add the chocolate to the heatproof bowl and stir until melted. 
• In a large mixing bowl, whisk together melted butter and both sugars. With an electric/stand mixer, go for a solid 3-5minutes so it is totally combined. Add in the eggs, one at a time and mixing in between. 
• Now, add the melted chocolate slowly and combine once again. 
• Add the flour, salt and cocoa powder, fold gently into the wet mixture with a rubber spatula or wooden spoon until just combined. Scoop into the muffin tin holes, no need to worry about filling close to the top, they don't rise much at all.
• Bake 20-25 minutes, until no longer wobbly. While still warm, create the indents by using a teaspoon measure, egg cup or end of a wooden spoon. Press into the middle, leaving tall sides. Let cool.

For the Filling

• Once the brownies have cooled, place a heaped teaspoon of marshmallow fluff into each. It will settle to fill the holes while you make the ganache.

For the Ganache

• Chop the chocolate up into small pieces if using block chocolate (chocolate chips are fine too). Place the chocolate in a heatproof bowl/jug.
• Heat the cream over a medium heat in a small saucepan. Once it has started simmering, pour it over the chocolate. Leave for 2 minutes, then whisk to create a thick, glossy chocolate ganache. Pour/spoon this over the brownie cups. Use the back of a spoon to spread over the top of the brownies.

For the Glaze

• Make the glaze by mixing the powdered sugar and milk. Put into a sandwich bag or piping bag with a very small nozzle. If using a sandwich bag, snip off a very VERY small corner to use as the 'nozzle'.
• Pipe on the looped swirls like in the images. Keep stored in the refrigerator until serving!