Remove the puff pastry from the freezer and allow it to thaw at room temperature while preparing the filling. You can also transfer it into the refrigerator the night before. Preheat oven to 350F/177C and grease a 12-count muffin pan with butter. You can also use a 24-count mini cupcake pan.

Next, prepare the filling. Preheat a large frying pan over medium heat and add the butter. Once the butter is melted, add in the diced smoked ham or bacon. Render the ham for 4 to 5 minutes, until it's golden brown. Remove the ham or bacon from the pan using a slotted spoon into a large bowl and keep the remaining fat in the pan. Next, add in the mushrooms and onion. Saute the mixture for 3 to 4 minutes, until the mushrooms are browned. Add the garlic and cook for 1 more minute.

Next, add the spinach into the pan. Toss it together with the mushrooms and onion and cook for another 2 to 3 minutes, until the spinach is wilted down significantly. Remove the mixture from the stove top and place into the same large bowl as the ham bits. Add the remaining ingredients: green onion, dill, parsley, egg, ricotta and parmesan. Use a large spoon to mix everything together until the mixture is uniform. Set the filling aside.

On a lightly floured surface, gently roll out each pastry sheet into a slightly large square. Cut each sheet into 6 equal squares; cut into 12 pieces if using mini cupcake pan. Gently line each muffin cup with pastry. Using a small spoon, fill the puff pastry generously with the prepared filling, filling all the way to the top.

Bake in preheated oven at 350F for 23 to 25 minutes, or until pastry is golden brown. Remove the tarts from oven and let cool for 5 minutes before removing from pan and serving. The filling will be extremely hot when the tarts come out of the oven! Be extra careful!