Preheat oven to 400°F (200°C) and generously grease a muffin tin with cooking spray.
In a bowl, mix hash browns with melted butter, salt, and pepper.
Press hash brown mixture firmly into the bottom and sides of each muffin cup to form a nest.
Bake for 15-20 minutes or until golden brown around the edges.
While the crusts bake, whisk together eggs, milk, cheddar, ham, and green onions in another bowl.
Remove muffin tin from oven and reduce temperature to 375°F (190°C).
Pour egg mixture into each hash brown cup until nearly full.
Return to oven and bake for 15-17 minutes or until eggs are set and tops are slightly golden.
Let cool for 5 minutes, then run a butter knife around each to release and serve.