In a bowl, cream together the butter and sugars until light and fluffy. Add the egg and vanilla and mix until combined.
Add the flour and salt, mix until you get a soft dough.
Add the chocolate chips, mix until combined.
With your hands, work the dough into a ball, gathering the dough from the side of the bowl.
Roll into a big sausage shape, wrap in cling film and chill in the fridge for 1 hour.
Preheat the oven to 180c fan. Line 2 baking trays with greaseproof paper (Or you can bake in multiple batches with 1 tray)
Divide the dough in half, leaving half in the fridge, take out one half and divide that into 28 small balls.
Space out on your baking trays (14 per tray)
Gently push in 3 micro eggs on the top of each ball, or broken up regular sized mini eggs if using and bake for 5 minutes.
As soon as you take them out of the oven put the tray on a cooling rack.
Whilst still warm, push in some colourful chocolate sprinkles then leave to cool completely.
Repeat for the remaining batches.
In a microwaveable bowl, break the chocolate and microwave for 30 seconds, stir, then repeat for a further 30 seconds. Once the chocolate starts to melt, microwave at 10 second intervals, stirring in between. Be very careful as white chocolate can burn easily. Once melted, leave to one side to cool.
Beat the butter until soft and creamy. Add the icing sugar and beat until combined. Once the chocolate has cooled down but not set, beat with the buttercream until combined.
Although you don't want your buttercream to be too soft, if you find it is too stiff, add a little milk.
You can either pipe or spoon the buttercream onto the inside of one cookie and use another cookie to sandwich it.
For the fudge, line a 9x9 tin with greaseproof paper or foil. Place Mini Eggs in a bag and bash with a rolling pin to break up (ideally you just want to break them only slightly). Place these in the refrigerator until needed.
In a microwaveable bowl, break up the chocolate and add the condensed milk.
Microwave in 30 second intervals until melted and combined.
Add the Mini Eggs and stir to incorporate.
Transfer the mixture to your tin and gently press to the edges.
Microwave 50g white chocolate in 30 second intervals until melted. Pipe or spoon this over the fudge. Sprinkle over some sprinkles and mini eggs then gently press down into the fudge. Refrigerate for 2 hours, then cut into squares.