With the rack in the middle position, preheat the oven to 230 °C (450 °F). Line a baking sheet with aluminum foil. Oil lightly. Set aside.
In a large bowl, combine breadcrumbs and milk. Set aside.
In a saucepan over medium heat, soften leek, garlic, pepper flakes and fennel in oil for about 10 minutes. Pour into the bowl with the breadcrumb mixture. Let cool. Add meat and egg and mix thoroughly. Season with salt and pepper. Shape into four large meatballs and place on the prepared baking sheet. Bake for 35 to 40 minutes or until meatballs are cooked through and golden brown. If necessary, finish cooking under the broiler, about 2 or 3 minutes.
Meanwhile, in a skillet, brown garlic in oil. Add tomato sauce. Cook for about 5 minutes or until sauce thickens. Remove garlic. Season with salt and pepper. Add basil and meatballs.
In a large pot of salted boiling water, cook spaghetti until al dente. Drain and toss with a little sauce.
When ready to serve, divide spaghetti among four plates. Make a cavity in the centre of the pasta. Top with a large meatball, add remaining sauce and sprinkle with grated Parmesan cheese.
Meatballs can be prepared the day before and baked the next day.
We prefer our version with Japanese breadcrumbs (panko), which makes a very tender meatball.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.