In a stand mixer, cream the butter, until smooth.
Mix in powdered sugar about ½ cup at at time, until smooth.
Mix in vanilla.
Mix in cream a tbsp at a time. Stop if it starts to look to wet. If it does become too wet, add additional powdered sugar.
Place the mixture in the fridge for about an hour. This will help it firm up and make forming the eggs easier.
Take about a tbsp of the mixture and form into an egg shape. Place on a non-stick pan or mat.
Once all eggs are shaped, place in the freezer for about an hour to help firm up the eggs.
While the buttercream eggs are in the freezer, melt the chocolate using your preferred method (i.e. double boiler, microwave, etc...). Once melted stir in about ¼ tsp of oil per cup of chocolate to help thin in for coating.
Once the chocolate is melted and the eggs are firm, dip the eggs into the chocolate to coat, then place back on a non-stick pan or mat.
Allow the chocolate to cool and firm up.