Preheat the oven to 170C / 340F. Grease a 9-inch baking pan with butter or line with baking paper.
Microwave the chocolate and butter together for 20 seconds. Whisk them well until melted and a lovely buttery chocolate mixture. Then Set aside to cool.
150 g dark chocolate, 130 g butter
In a bowl, mix eggs and sugar well using an electric hand mixer or stand mixer on high speed until you have a thick pale mixture.
3 large eggs, 245 g caster sugar
Stir in the slightly cooled chocolate mixture and vanilla extract, stir well until combined.
1 tsp vanilla extract
Fold in the flour and cocoa powder and gently mix until combined. Now you have a lovely fudgy brownie mixture.
45 g cocoa powder, 90 g plain flour
Pour the mixture into the baking pan and sprinkle the chocolate eggs on the top then bake for 25-30 minutes.
200 g chocolate mini eggs
Notes
Let the brownies cool completely before taking them out of the baking pan.