Cream butter, vanilla, and corn syrup together.
Gradually add powdered sugar a little at a time until fully incorporated.
If you want the creamy/liquid center like the real Cadbury Eggs add the Invertase (They will liquify within 2-3 days). If you don't want to purchase Invertase, you can still make this recipe just fine. They'll still have the Cadbury egg flavor, it will just be more solid.
Transfer around 1/3 of your filling to a separate bowl. Add yellow food coloring until it reaches your desired shade.
Refrigerate white and yellow filling for around 30 minutes.
Line a baking sheet with parchment paper. Roll yellow filling into 1 inch balls and place them on the parchment paper.
Return yellow balls to the fridge until firm (around 30-45 minutes).
Flatten white filling mixture into a circle. Place your yellow ball in the middle, and wrap the white around it into an egg shape. Return to parchment paper. Place in fridge or freezer until solid.
Melt chocolate in the microwave for 30 second increments until smooth.
With a fork, dip your eggs into the melted chocolate until covered completely.
Return chocolate covered eggs to the parchment paper and refrigerate until set.