Preheat your fan oven to 160˚C (325˚F) or 180˚C (350˚F) if you're not using a fan oven. Grease and line with baking paper an 8x8-inch (20x20-cm) baking tin.
Roughly cut the chocolate mini eggs with a knife; leave some eggs whole, it's perfectly fine.
In a medium-sized bowl, sift and combine the flour and cocoa powder. Set aside.
Place the chopped chocolate (or chocolate chips) and diced butter into a heatproof bowl and melt over a bain-marie (a pot of simmering water). Make sure the bowl doesn't actually touch boiling water. Stir occasionally with a silicone spatula, so it combines and melts evenly. Once it's done, set it aside to cool a little bit.
In a bowl of your stand mixer fitted with the whisk attachment, whip together the eggs, both sugars and salt, until pale, fluffy and doubled, almost tripled in volume. You can't really overmix this, so let it beat on high for a minimum of 5 minutes. I usually let it whip for around 8 minutes.
Next, set your mixer to medium-low speed and slowly, in a steady stream, pour in your melted chocolate-butter mixture. Add the vanilla and mix until everything is combined.
Add the dry ingredients and mix on low speed, just until combined. You can also use a spatula in this step and just fold the dry ingredients.
Add about 160 g of chocolate mini eggs to the batter and fold them in the batter with a silicone spatula.
Pour the brownie batter into the prepared pan, leveling the top with a spatula or a palette knife, so it reaches all corners.
Sprinkle the top of the brownie with the rest of roughly chopped mini eggs.
Bake in a preheated oven for about 30 to 35 minutes. Halfway through the baking, carefully drop your pan on the counter a few times to deflate it and create an even top layer with the fudgy inside.
Once they're done, place the pan on a cooling rack and let the brownies cool completely before cutting into it.
If desired, serve with a dollop of freshly whipped cream and a cup of coffee.
If you don't have a stand mixer, you can use an electric hand mixer.
If you still don’t own one, I advise you to buy a kitchen scale – they’re cheap and easy to use, and always guarantee the same results in baking. :)
Not all ovens are the same, check the brownie at the 25- minute mark, then adjust the time accordingly. Don't overbake it!