Fill a large pot or sous vide container to the minimum water line with hot water.
Attach the sous vide to the pot/container and set it to 172 F (78 C).
While the water is heating up, use your fingers to coat the inside of 10-4 oz (125 ml) jelly jars with a very thin layer of butter. Alternatively, coat them in cooking spray.
Place 1 tablespoon diced ham and ½ tablespoon grated cheddar cheese in the bottom of each jar. Add a few slices of green onions.
Crack the eggs into a medium mixing bowl and add the cream/milk. Season with salt and pepper, then whisk until the egg mixture is well mixed and frothy.
Pour egg mixture into the jars, filling each one ¾ full. Cover each jar with the lid and metal ring, tightening slightly. Screw them on until you feel resistance, then back off slightly.
When the water reaches 172 F (77.8 C), place the jars upright in the water. Stack if necessary.
Check to make sure no jars are leaking and air is able to escape the jars. Cook eggs at 172 F (78 C) for 1 hour.
Use tongs to remove them from the water bath wipe the jars dry. Serve egg bites in jars or remove them and serve on plates.
For make ahead egg bites, submerge jars in an ice bath to cool the eggs quickly to room temperature, then refrigerate.
