Preheat the oven to 350 degrees F. Lightly butter or oil a 12-inch cast iron skillet or 9x13 casserole dish.
Heat another large 12-inch skillet over medium-high heat. Add one tablespoon olive oil. Once hot, add minced garlic, finely chopped mushrooms and onion. Add additional veggies here if desired. Sprinkle with ¼ teaspoon salt. Saute 6-8 minutes, or until mushrooms are soft. Drain off excess liquid.
Add chopped parsley, rosemary, thyme, oregano. Saute another 30 seconds to bloom the herbs. Add extra oil as needed. Add the crushed tomatoes with juices, sugar and black pepper. Bring to a rapid simmer over medium high heat. Reduce to a low simmer over medium-low heat. Simmer for 15 minutes then turn off the heat. Taste for salt.
Meanwhile, cook the spaghetti to al dente in well salted water according to package instructions. Once cooked, drain the pasta. Transfer spaghetti to the pasta sauce. Stir in ¾ cup shredded mozzarella.
Transfer spaghetti and sauce mixture to the oiled cast iron pan. Top with remaining ¾ cup of shredded mozzarella.
Bake at 350F for 20 minutes, or until mozzarella is golden and bubbling. Remove from the oven and let rest 5 minutes before slicing to serve. Enjoy!
Fresh herbs: Rosemary, oregano and thyme can each be replaced with 1 teaspoon dry herbs.
Extra veggies: Add carrots, squash or even peas for extra veggies. You can blend the pasta sauce after simmering if you prefer a "hidden veggie" sauce. Be careful if blending as it will be very hot.
Store refrigerated in a closed container for up to 5 days. To freeze, cover the cooled casserole with foil and freeze for up to 3 months.