Place the custard, chocolate, peppermint extract and salt into a medium sized sauce pan and place over a low heat.
Stir the custard until all the chocolate is melted and the mixture is smooth. Leave to one side to cool.
Make the whipped cream: Place the cream, sugar, peppermint extract and a couple of drops of food colouring into a large bowl and mix gently to check the colour. If required, add more food colouring and stir it gently.
Once you're happy with the shade of green, whisk the cream until stiff peak. You want to be able to pull the whisk out of the mixture and have the peak stay up.
Crumble the brownies into a small bowl, crumbs and small chunks are fine.
Take 4 individual sized trifle dishes/jars/glasses and place a layer of brownies on the bottom of each jar; around 1tbsp of brownie pieces.
Spoon 2 tbsp of the custard mixture onto the brownies, then spoon 2-3 tbsp of whipped cream on top of the custard. Smooth gently into an even layer, try and cover the custard but if you don't completely, it's totally fine. These will still look awesome even if you just dump everything into the glasses!
Place another layer of brownies, custard and then cream. The 6 layers filled my glasses, but repeat if you have supplies left and room in your glasses.
Finish with a sprig of mint and a sprinkling of leftover brownie crumbs.
Mini Mint Chocolate Trifles will keep covered, in the fridge, for 2 days.