Spinach, mushroom, and onion mix: add 2 tablespoons of olive oil to a medium pan over medium heat. Once the oil is shimmering, add minced garlic and cook for 2 minutes. Then add the mushrooms and cook for about 3 or 4 minutes. Season the mushrooms with just a pinch of salt and ground black pepper.

After the mushrooms have softened a little add the thinly sliced onion and stir them in with the mushrooms. Cook for about 4 minutes until the mushrooms and onions are softened, but not turned into mush. 

Add a couple of handfuls of spinach at a time and stir it in with the mushrooms and onions. At first, it will look like there is way too much spinach for your pan, but it will wilt and shrink down allowing you to add a couple more handfuls.

Add a pinch or two of salt and ground black pepper and keep adding and stirring until all the spinach is in the pan. 

Cook for between 5 and 10 minutes or until all the spinach has been added and everything is soft. Remove the spinach mix to a plate to cool or to a sealed container in the refrigerator until it's time to make the sandwich.

Roasted tomatoes: Slice the Roma tomatoes and place them on a sheet pan with at least a half inch of room between each one. Paint or spoon a little olive oil on top of each tomato and then sprinkle a tiny pinch of salt and ground black pepper on top of each tomato. Bake them at 400 degrees F (205 C) for 15 to 20 minutes or until the tomatoes are soft but not falling apart. Remove them to a plate or a sealed container until it's time to make the sandwich.

Compound butter: in a small bowl combine all ingredients and using a spoon or spatula mix everything very well. 

Store in a sealed container or wrapped in plastic wrap in the refrigerator for up to a week. 

Garlic bread: spread a thin layer of compound butter on the bottom slice of your sandwich roll. Place the buttered piece of bread under your broiler for 3 to 4 minutes or until the edges of the bread are turning brown and the butter is very melted. If you do not have a broiler, you can cook the garlic bread in a 375-degree F oven for 10 to 15 minutes to melt the cheese and crisp up the bread. 

Sandwich assembly: on top of the garlic bread layer the following ingredients: sliced mozzarella topped with pizza sauce, a couple of big spoons of cooked spinach mix, then the roasted Roma tomato slices. Finally, top everything with shredded cheddar cheese and a sprinkling of grated Romano or Parmesan cheese. Cap everything off with the top of the sandwich.

Panini process: cook the sandwich in a lightly oiled panini press until the bread gets crusty and browned. If you do not have a panini press, you can use a hot cast iron skillet with another skillet on top of the sandwich, pressing it down. Add a little oil to the top of the sandwich and to the bottom pan before cooking. This two-pan method will griddle one side and you will have to flip the sandwich, but it will work.