Line a small rectangular baking tray or cake tin with baking parchment. If you don’t have any, tin foil also works.
Place the digestive biscuits in a strong freezer bag. Using a rolling pin, bash the biscuits to roughly smash them.
Break or chop the milk chocolate and dark chocolate into chunks and place in a large microwave safe bowl. Add the butter and golden syrup.
Heat in the microwave for short bursts of around 30 seconds, stirring in between, until the chocolate has almost melted. Be careful not to overheat or burn the chocolate.
Once the chocolate is melted, stir with a spoon until all the ingredients are fully combined and the mixture is smooth.
Pour the smashed digestive biscuits into the bowl and mix together until the biscuits are completely coated in the chocolate mixture.
Add half of the mini eggs to the bowl and mix in with the rest of the ingredients.
Tip the fridge cake mixture into your lined tin, spread it around and push it down with the back of the spoon to press it into the tin.
Scatter the remaining mini eggs on top, then carefully push them all into the fridge cake, working quickly before it sets.
Pop the tray into the fridge and leave to set for around an hour. Once the fridge cake has set hard, take it out and cut into pieces.