1. Grease a 9×13 inch pan and set aside. 
  2. Place olive oil in a skillet over medium heat. Add Italian sausage and cook until starting to brown, breaking up with a spoon as it cooks. Add mushrooms and onions and cook until veggies are soft and sausage is cooked through. Add spinach and cook until just wilted. Remove from heat. 
  3. Crack eggs into a large bowl. Add half and half, salt, pepper, bagel seasoning and dijon mustard. Whisk until smooth. 
  4. Place the bottom halves of the croissants in the prepared dish and spoon the sausage mixture over the top. 
  5. Sprinkle the grated Kerrygold® Aged Cheddar over the sausage mixture. 
  6. Pour the egg mixture over the top of the sausage and croissant bottoms. Place the remaining croissant halves on top, pushing them down slightly to immerse in the egg mixture. Cover with foil and let sit for an hour at room temperature so the croissants can soak up the egg mixture. 
  7. Preheat the oven to 375°F and bake covered for 30 minutes. Uncover and bake for an additional 20 minutes or until eggs are set. 
  8. Cool for 10 minutes, garnish with parsley, slice and serve. 

Recipe by Garnish with Lemon.