Preheat oven to 375°F if using metal baking pan. Grease 9x13 inch baking pan. If using glass/ceramic or making overnight, place pan the oven at the same time you turn on the oven so that it warms up slowly with the oven to prevent shattering glass. See recipe notes for overnight instructions.
Place frozen hashbrowns into baking pan, then sprinkle half (1½ cups) cheese on top. Sprinkle diced ham over cheese and gently mix them together in the pan.
In a mixing bowl, whisk together the eggs, milk, and melted butter and mix well, until smooth. Add in all spices and mix well. Pour over hashbrown, cheese, and ham mixture in pan. Gently mix together until combined.
Sprinkle remaining 1½ cups of cheese over the top of the casserole and bake for 35-40 minutes, until set in the middle and no longer liquid. Sprinkle the top with green onions, slice and serve warm.
Notes
If using cold ceramic or glass bakeware straight from the refrigerator, do NOT put it in a hot oven! It may shatter glass. It can also become cold if you put frozen hashbrowns into it. To prevent shattering, I recommend putting it in the oven at the same time you turn on the oven so that it warms up slowly with the oven. Overnight instructions: Make recipe as directed, then cover and refrigerate overnight.When ready to cook, preheat oven to 375F if using metal pan or if using glass or ceramic pan, place casserole dish in the oven the at the same time you turn the oven on. Bake for 45-50 minutes until middle is set and no longer liquid.