Pre-heat your oven to 100C Fan/225F/Gas Mark ¼, and line two or three baking trays (depending on size) with greaseproof paper
Finely grate the dark chocolate and stir the cocoa powder into it
Whisk up the egg whites and cream of tartar in a food mixer until stiff peaks form, they will hold their shape but still be foamy.
Keeping the mixer going, add the vanilla extract and slowly add caster sugar a spoonful at a time. Once stiff peaks form turn the mixer off, the meringue will be thick, glossy and hold it's shape very well
Fold the chocolate and cocoa powder mix into the meringue
Put the meringue into a piping bag with a star nozzle and pipe out nest shapes onto the baking tray. Start by piping a circle, then pipe a ring on top of the circle. Or you can dollop the meringue onto the baking tray and use the back of a spoon to create a dent in the centre
Bake the meringue nests for 1 hour and 30 minutes. To avoid the meringue from cracking turn the oven off and do not open the door until the oven is fully cooled down
Whip up the double cream with the icing sugar and vanilla, then spoon it into the middle of each nest, add 3 Mini Eggs per nest and add some dark chocolate sprinkles, or grated dark chocolate curls if you like
Store in the fridge and eat within 2 days