Crush most of the mini eggs by popping them in a bowl and gently bashing them with the end of a rolling pin. Reserve some whole for decoration.
Melt the chocolate in the microwave or in a bain-marie. Whichever way you melt it, keep an eye on it and don't leave it to melt for too long or it will seize.
Pour the condensed milk into the melted chocolate and a pinch of salt and mix well.
Add most of the crushed mini eggs to the fudge (reserving some for decoration) and mix well.
Pour the fudge into the lined brownie pan and smooth out with the back of a spoon.
Press whole and crushed mini eggs into the top of the fudge, then add sprinkles for extra decoration and pop in the fridge for an hour to set (it could set faster).
Once set cut it in 5 rows, each way to give you 25 pieces or fudge or you could cut less rows for bigger pieces.
Enjoy!
Notes
Baking paper - leave an overhang of baking paper when lining the pan for easy removal.
Chopping mini eggs - don't try to chop the mini eggs with a knife, the shape, smoothness and thickness of the shell make it dangerous and too easy to cut yourself, so pop them in a bowl and bash gently with a rolling pin. Don't have a rolling pin, bash them with a can of tomatoes.
Melting chocolate in the microwave - Melt it for 30 seconds, check it, give it a stir and then give it 10-second blasts until it has melted. DON'T overcook it. You have to keep an eye on it. Remember it's fast.
Melting chocolate in a bain-marie - melt chocolate in a bowl suspended over a pot with simmering water. Make sure the bowl is big enough to sit on top of the pot and above the water. If the bottom of the bowl touches the water there is a good chance the chocolate will seize and go grainy.
Storing the fudge - wrap it in non-stick baking paper (you can pop a slice between the layers to stop it from sticking). Store it in an airtight container for 4-5 days.
Size matters - cut the fudge pieces as big or small as you like. It cuts very easily.