In a bowl, combine the beef, egg, breadcrumbs, cheese, and garlic at room temperature about 68°F. Mix with your hands for 60 to 90 seconds using a folding motion, like turning the mixture over itself. Don't squeeze. It should feel soft but hold when pressed. If you overwork it, the meat turns tight and the meatballs cook up dense. Shape into balls about 1.5 inches wide, rolling lightly between your palms for 20 to 30 seconds each. You'll see a slightly rough surface and that's right. Smooth means overmixed. Let them sit at room temperature for 5 minutes so they cook evenly. If they go in cold, they can split before they brown.

Heat olive oil over medium heat, about 5 on a 10 dial, for 2 minutes until it shimmers. Place the meatballs in with space between them and leave them untouched for 2 to 3 minutes. You should hear a steady sizzle and see the bottoms turning deep golden. Turn them gently with tongs every 2 minutes for 8 to 10 minutes total. Rotate, don't poke. The crust builds flavor and keeps them together later. Miss this and they can fall apart in the sauce. (I used to flip them too soon and they tore. Waiting fixed it.)

Lower the heat to medium-low, about 4 on a 10 dial. Add onion and cook for 5 to 6 minutes, stirring every minute until soft and lightly golden. Add garlic and stir for 30 seconds until you smell it bloom. Pour in the tomatoes and bring to a gentle simmer around 200°F. Small bubbles should rise slowly, not boil. Let it cook for 12 to 15 minutes, stirring every few minutes and scraping the bottom once at minute 6. The sauce thickens and coats the back of a spoon. If it boils too hard, it turns sharp and can separate.

Bring a large pot of salted water to a rolling boil at 212°F. Add the spaghetti and stir right away for 10 seconds so it doesn't clump. Cook for 8 to 10 minutes, giving it a quick stir at minute 4. At minute 8, pull a strand and bite. It should have a slight bite in the center. That's al dente. You'll feel resistance but no crunch. Overcook it and it goes soft and won't hold sauce. Drain but don't rinse so the starch stays on the surface.

Add the drained spaghetti straight into the simmering sauce over low heat, about 3 on a 10 dial. Toss with tongs using a lifting and folding motion for 1 to 2 minutes. Keep the pasta moving so it absorbs the sauce evenly. You'll see the strands turn glossy and evenly coated. If it looks dry, add a splash of pasta water and toss again. Skip this step and the sauce just sits on top instead of soaking in.

Return the meatballs to the pan over low heat, about 3 on a 10 dial. Spoon sauce over them and let everything warm together for 5 minutes. The sauce should gently bubble around them, not boil. Sprinkle grated cheese and let it melt for about 1 minute. Add torn basil right at the end and give one light toss. You'll smell it immediately. Add it too early and it fades into the sauce instead of staying bright.