Place chocolate, condensed milk, butter, vanilla paste and salt into the Thermomix bowl and cook 40 min/70°C/speed 1.
Meanwhile, line a square 18cm tin with a removable base with baking paper that comes above the sides of the tin for easy removal. When the chocolate fudge is done, pour into the tin and tap on the bench to level.
Working quickly, decorate the entire slice with as many of the toppings you can fit onto it. The more the merrier. The chocolate callets will melt with the heat of the fudge, but that is ok. So start with the biscuits/cookies and just keep going until the entire surface is covered. I even broke up some of the red velvet melting moments and used the crumbs to decorate too. The sky is the limit!
Leave to set at room temperature for a couple of hours before transferring to the fridge.
To serve, cut into small pieces.