Preheat oven to 350° F. Line a muffin tin with 12 parchment paper liners or silicone liners.
Distribute the cubed sausage pieces evenly among the cups. Then repeat with the white onion, spinach/kale, minced garlic, and Italian seasoning.
Whisk the eggs in a medium bowl. Add in the nut milk, sea salt, and fresh ground black pepper. Whisk until combined completely.
Pour the egg mixture into the cups, filling each cup almost completely.
Bake at 350° F for 30 minutes, until cups are no longer jiggly, no longer appear wet, and are starting to brown around the edges. (After 30 minutes, I turned my oven off but left the muffin tin in the oven until they appeared dry). Serve warm and enjoy! Store leftovers covered in the refrigerator for up to five days.