In a medium microwave-safe bowl, melt the peanut butter and chocolate and stir until it is well mixed. Add the powdered sugar to the chocolate and peanut butter mixture.
In a separate mixing bowl, pour 4 cups of the cornflakes and stir in the peanut butter & chocolate mixture and mix until the cornflakes are evenly coated.
Add the remaining cereal 1 cup at a time until you reach your desired consistency. (For this batch, 7 cups were used but some require more, some require less).
Scoop the cornflake mixture into lined muffin tins and shape into a nest using your fingers (careful! It may be hot!) or the back of a spoon.
Place 4 mini eggs into each nest.
Refrigerate the peanut butter nests for at least 30 minutes before serving or digging in so that the chocolate has time to set properly.