1. Preheat your oven to 375°F (190°C). This temperature crisps the bread nicely without drying it out.
2. Prepare the bread bowls: Cut the tops off the bread rolls and hollow out the centers, leaving about a 1/2-inch thick shell. Set aside both the hollowed bread and the tops for later use.
3. Cook the spaghetti: Bring a large pot of salted water to a boil and cook the spaghetti according to package instructions until al dente, usually about 8-9 minutes. Drain and set aside.
4. Make the garlic butter spread: In a small bowl, mix softened butter with minced garlic and a pinch of salt. Spread this mixture generously inside the hollowed bread bowls and on the cut tops.
5. Bake the bread bowls: Place the bread bowls and tops on a baking sheet and bake for 10 minutes, or until golden and slightly crispy. This step ensures they hold up well to the sauce and pasta.
6. Prepare the spaghetti sauce: While bread bowls bake, heat olive oil in a medium skillet over medium heat. Add chopped onion and cook for 3-4 minutes until translucent.
7. Add minced garlic and cook for another 30 seconds until fragrant, being careful not to burn it.
8. Pour in the crushed tomatoes, stir in Italian seasoning, red pepper flakes (if using), salt, and pepper. Let simmer gently for 10-12 minutes until slightly thickened.
9. Stir in Parmesan cheese to enrich the sauce and adjust seasoning to taste.
10. Combine spaghetti and sauce: Toss the cooked spaghetti into the sauce until evenly coated.
11. Assemble the bowls: Spoon the saucy spaghetti into each garlic bread bowl, filling them generously.
12. Sprinkle shredded mozzarella on top of each bowl and return to the oven for 5-7 minutes, or until the cheese melts and bubbles.
13. Garnish and serve: Remove from oven, sprinkle chopped parsley on top, replace the bread tops on the side, and serve immediately.

One tip I picked up from my early cooking days—after oversalting a pot of chili—was the importance of tasting as you go. Don’t be shy about adjusting the seasoning throughout, especially the salt and pepper. It really makes a difference.