Preheat the oven to 350°. Line a 8×8 pan with parchment paper. Set aside.
Melt the butter, whisk in the cocoa until there are no more lumps.
Pour the butter and cocoa mixture into a large bowl. Add in the sugar and mix using an electric mixer until well combined. It will be grainy.
Mix in the eggs and vanilla thoroughly.
Add the Flour and salt to the bowl and combine. The batter will be very thick.
Spread the batter into the 8×8 pan.
Press the Cadbury mini eggs into the batter slightly. Note: to make cutting the brownies easier, try to avoid placing an egg where you will be cutting.
Bake at 350° for 25 minutes.
Allow to cool for 5-10 minutes before cutting.