Preheat oven to 425 degrees
Brown Italian sausage in a medium skillet and once it is nicely browned, transfer it into a bowl and set aside
In the same skillet, cook the diced onions over medium heat, scraping the browned bits from the Italian sausage from the bottom of the skillet
Once the onions are softened, add the mushrooms and continue to cook until the mushrooms are softened as well
Transfer the onions and mushrooms to a bowl and set aside
Add spinach to the skillet over medium heat for two minutes or until it has wilted slightly. Transfer into a bowl and set aside
Lightly flour a large cutting board and roll out the puff pastry slightly larger than it was in the packaging
Run a knife to score a line about 3/4 of an inch inside the boarder of the puff pastry
Using a fork, gently prick holes all over the puff pastry to the inside the boarder
Make an egg wash by whisking one egg and one teaspoon of water together in a small bowl and brush this egg wash around the boarder of your puff pastry
Top the puff pastry with shredded cheese, cooked Italian sausage, onions, mushrooms, wilted spinach and sun dried tomatoes
Bake at 425 degrees for 15 minutes
Remove from the oven and crack 4 large eggs onto the tart
Return the tart to the oven and bake until the eggs are set to your preference
Garnish with additional shredded cheese and finely diced spring onions